The most extensive playbook on using Slack to the utmost
Standuply team put 500 hours in this book. Learn more ⟶

Learn How To Use Slack Effectively In 2019

We spent 500 hours to make a fantastic and super useful Slack Guide. Hopefully, this is the only guide on how to use Slack and FAQ you will need to supercharge your work.

And let us be clear about something: this is NOT a post with a long description of all the features, see Slack Help Center for that.

, we share all of our experience and best practices on how to improve the way you work in Slack.
If you're just getting started, you'll find everything to quickly learn how to use Slack in Chapters 1 - 3.
Since there is no official Slack FAQ, we answered 40 most burning questions in Chapter 4.
For advanced Slack users, we uncover best practices on how to use Slack to maximum efficiency in Chapters 5 and 6.
Don't have time to read it right now?
Let us send you a PDF copy so you can read this guide when it's convenient for you.
It takes 5 seconds, just let us know where to send it.
So if you're looking to kick off 2019 year strong, you'll love this guide.
Let's dive right in.
This guide was made by the team who built Standuply, the #1 Project Management App for Slack.
About us
For easier navigation use arrows: down arrow ↓ for next the chapter, up arrow ↑ for the previous chapter.
Chapter 1
Why use Slack?
What is so unique and special about Slack? Why do people use it for team communication and collaboration? Well, Quora has it covered: #1, #2, #3. Thousands of people have also left their 5-star reviews at Capterra.

With more and more distributed teams, it is becoming important to ensure that there is clear communication between everyone in the team. This is where Slack comes to the rescue. It is an awesome collaboration tool that enables teams to do literally anything in one place.

Slack facilitates clear and open communication, promoting Agile development. No wonder even picky developers love Slack, and not only them.

Slack too loves its users building all the features a team of any size might need for productive collaboration:
  1. A single workspace for the whole team.
  2. Channels for topic-centered discussions.
  3. Audio and video calls.
  4. File sharing and search.
  5. Apps and integrations.
Speaking of Apps and Integrations, Slack nailed it. It's like an operating system with thousands of apps to streamline work processes and save our precious time (i.e., Standuply for better standup meetings in Slack).

With Slack, a team reduces internal email, increases transparency, and everyone is on the same page. Slack is compatible with various platforms, and it has seamless synchronization to ensure you don't miss anything.

Seems like Slack is really worth trying out.
Source: Slack Technologies Inc., Youtube channel.
Slack Workspace
If you don't know your workspace URL, Slack can help you find workspaces you're eligible to join based on the work email address you specified while registering.
Every Slack team has its own workspace. A Slack workspace is a space that brings together all the channels and chats of a company, where all communication, file sharing, and conference calls take place.

Each workspace is a closed space for a group of people, usually employees of one company.
However, Slack is often used as a forum for folks from different companies. We've been collecting all kinds of Slack forums since 2016. See our latest list of 2000 Slack groups.

You can join several workspaces and switch between them if necessary. Each workspace has its own channels, chats, and rules set by the particular team in that space.

To join a Slack workspace, you need an email invitation or you can create an account on the workspace by yourself. There are several ways to do this:
  1. Receive and accept an email invitation from a member of the workspace and sign up by clicking the link contained in the email invitation.
  2. Join a workspace using your work email address. Slack is often tied to a company domain, which means that any new person in an organization can join on their own. You can do it here.
Do you want to create your own workspace and invite a team there? It's as easy as pie:
    1. Create a workspace by following this link - https://slack.com/create
    2. Then invite members from the invitations page. Click your Team Name within Slack to open your Team Menu. From there, select the option to Invite people.
    For Admin
    Source: Slack Technologies Inc., Official website.
    Download Slack
    Slack is available on different platforms as a native app. It can also be used as a website, which is quite convenient. However, the app comes with more settings and it is faster to switch between different workspaces in the app.
    You can download Slack apps via the links below:
    Even if you have multiple devices, Slack will synchronize them in real time.
    Slack Guest Access
    Slack Guest Access is one of the remarkable features in Slack. It's convenient when inviting a temporary consultant or freelancer to the team. Guests have limited access to the entire workspace or to one channel.

    If you are invited as a guest, you only need to join via the invitation link in order to gain access to the particular Slack workspace.

    Guests are divided into two types: Single-Channel Guests (have access to one channel) and Multi-Channel Guests (have access to multiple channels at once).
    Multi-Channel or Single-Channel Guests can be invited to your workspace just like regular members via the Invitations page. For step-by-step instructions, see the link.
    For Admin
    Main Actions in Slack
    Slack comes with so many useful features. But first, let's go through the basic actions and commands for communicating in channels and in direct messages. Details on how to use Slack to send messages and communicate in channels are described in the Slack Help Center.

    The popular Slack commands are @channel (notifies all members of a channel), @here (notifies only the active members of a channel) and @username (notifies the person mentioned). Below is how it all works.
    Your action
    What will happen
    You write a message in a public channel.
    All members of that channel will see it, including those who will join the channel later on.
    You post a message to a private channel.
    Only members of that channel will see it and no one else.
    You post a message to someone in direct messages ('DM').
    Only that person will see it.
    You post a message to a user group.
    Only members of that group will see it.
    You mention someone in a channel with the @ symbol, but the person isn't in that channel.
    That person will NOT receive a notification but Slackbot will ask you if you want to invite the person to join the channel. See more.
    You mention someone in a private channel but the person isn't in that channel.
    That person will NOT receive a notification, but Slackbot will ask you if you want to invite the person to join the channel.
    You mention someone in a direct message or in a user group.
    That person will NOT receive a notification, and you will NOT be able to invite him to DM or group. But you can do this differently.
    You pin a message in a channel.
    Every member of that channel will see it. See more.
    You star a message or channel.
    Only you can see it. See more.
    You post a message with a hashtag and the name of a channel (for example #general)
    The name of that channel will be highlighted in blue. When you click on it, you can join the channel.
    You send a message with a hashtag and the name of a private channel (for example #privatechannel)
    The name of that channel will NOT be highlighted in blue. When you click on it, you will NOT be able to join the channel.
    These are the basic actions in Slack. However, there are many more of them. If you want to explore them all, here are additional reads:
    If you still have any questions on actions in Slack, don't hesitate to go back to this page and check the table above.
    Chapter 2
    Slack offers a number of simple settings that would enable you to explore a team's list of members with information who does what. You can create your virtual business card on Slack and even set your availability work schedule.
    Setting up Your Slack Profile
    You can set the following parameters in your profile:
    • Name
    • Display Name
    • Position
    • Personal contacts
    • Time zone
    • Photo
    • Status
    • Availability
    Whether you're OOO on vacation or out on maternity or paternity leave, you can signal this to your co-workers by adjusting your last name on Slack (i.e. Jane Smith OOO where Jane is the first name and Smith OOO is the last name).
    Admins can customize the required fields for a user profile.
    For Admin
    Below, we will describe how some of these options are configured. In general, almost all of this can be done in one place. To cut the long story short, it is done as follows:
    • Click on your name in the top left corner of your screen
    • Select Profile & account
    • Click Edit Profile

    Fill in all the required fields and click Save Changes.
    Choosing Display Name
    The Display name is the name that your workspace members will use to mention you in channels. It can be short or long, real or a nickname.

    You can change your display name in your Profile settings as follows:
    • Click on your name in the top left corner of your screen
    • Select Profile & account
    • Click Edit Profile
    Change the Display Name and click Save Changes
    Use names that resemble your real name, else your teammates might find it difficult remembering who "@fluffykitten" or "@bigboss" is.
    Slack Profile Picture
    This is also done in your profile settings:
    • Click on your name in the top left corner of your screen
    • Select Profile & account
    • Under Profile photo, click the image to change your profile photo
    • Choose an image to upload
    • Adjust the crop for your photo (cut/edit)
    • Click Save Changes

    Remember that your Slack profile picture should be a minimum of 512x512 pixels and a maximum of 1024x1024.
    You can use any image as your profile picture if you want to have some fun. However, for your daily work, it's better to use real pictures for your teammates to easily identify you in channels and online meetings.
    What's your status?
    With your status, you can always tell your teammates what you are doing at the moment and how quickly you can reply to messages. Slack offers you several ways to do it: through your Slack status or through the availability feature (see below).
    To set a status, you can choose one of the five suggested options or enter your own. In addition, you can add an emoji to it, which will show next to your display name in chat rooms.
    • Click on your name in the top left corner.
    • Click Set a status
    • Click the smiley face icon to select an emoji, or select from one of the suggested statuses.

    Or enter your own status, then click Clear after and select a time period after which the status will disappear
    You can still automatically set your Slack status if you want. All you need to do is connect your calendar, to-do list, and other tools to Slack with Zapier. Read more here.
    Source: Slack Technologies Inc., Help Center.
    Setting up Availability
    The colored dot next to your display name indicates if you're available in Slack. The possible modes are:
    • Active
    • Away
    • Connecting
    • Do Not Disturb
    Away status can be set by Slack automatically or you can set it manually. There is a chance you might want to set yourself Away so that you could avoid unnecessary distractions.
    To set your availability to Away:
    • Click on your name in the top left corner.
    • Click Set yourself to away
    When you set Do not Disturb status, all notifications and @mentions will be paused. See how to do it in the guide below.
    For Admin
    Source: Slack Technologies Inc., Help Center.
    Choosing Your Time Zone
    Nowadays, many teams are distributed. That is why collaboration inside Slack needs to be properly synchronized. This applies to reminders and Slack bots.

    For example, when Standuply runs a standup meeting by reaching out to team members by their time zone it's essential that everyone set their time zone right. Otherwise, people would get a message from the bot at a wrong time.

    To do this, you need to set your time zone as follows:
    • Click on your name in the top left corner of your screen
    • Select Preferences
    • Select the Language & Region tab
    • Choose your time zone
    Chapter 3
    Improving Productivity with Slack Apps
    Slack apps are like the apps in your smartphone. There is even an app store where you can find and install a Slack app in your workspace.

    All of 2,000 Slack apps that are publicly available are widely different. You have tiny fun apps (Giphy, Lunch Train), advanced project management apps (Standuply, Kyber) and 3rd party integrations (Google Drive, Dropbox).

    When adding apps to Slack, you can transfer all your work to Slack and stop juggling all those open windows on your computer screen.
    Slack App Directory
    Slack App Directory is an app store for Slack, where you can see apps approved by Slack and choose an app by category (for example, Analytics, Project Management, Productivity, etc.).

    In addition, you can explore apps right in Slack: click on (+) sign in the left corner of your screen near the Apps section. From there you'll be able to search and browse apps without leaving Slack.
    To explore installed apps, click on your workspace name in the top left corner, and select Administration -> Manage apps. If you want to create a list of approved apps for your workplace, here's a guide on how to do that.
    For Admin
    How do I install an app from Slack App Directory?
    When you have found an app you would like to add to Slack, just click Install button under the app's icon in the App Directory. Then follow the instructions to launch the app.
    If the app installation isn't available directly from the Slack App store there will be Visit Site to Install button. Click it and then install the app from its website.
    Sometimes admins can limit the list of apps available to members for installation. If the app you want is not listed in the approved list for your workspace, you may send a request to the Admin to install it: click the Request button below the app's icon and then click Submit request.
    What are the best Slack apps and how do I choose an app?
    We strive for Standuply to be among the best apps for Slack. And we have the proof: Slack Corp. itself uses Standuply for their standup meetings. Watch video about Standuply below.
    As we've already mentioned, the Slack App Directory features almost any app you need for your work. Apps there are ranked by popularity, so the higher the app the more users it has.

    In general, if an app is listed on the first page of any category in the Slack App Store it's worth checking out.

    You can also look at the Brilliant Bots category. There, you'll find handpicked apps by Slack Corp that are most popular and useful.
    Looking for Slack Apps for Product Management? See our other post: 100+ Slack Apps and Integrations for a Product Manager.
    What is custom Slack integration?
    Custom Slack integrations are similar to the other apps. However, custom integrations are created inside your team using a special protocol from Slack (API).

    Usually, these are the integrations that simplify your internal work processes. And you can create something just for fun. For example:

    1. A bot that answers your specific questions. Some of the questions could be: who is in the office today? what's the password for the office Wi-Fi?
    2. A bot that shows sales statistics (leads, calls, etc).
    3. You can even make a bot that can open or close doors, or turn on a coffee machine via a slash command.
    For more instructions on how to create custom integrations, check out the developer section on the Slack website.
    For Admin
    How do I remove an app from Slack?
    The process of removing apps and custom integrations is a bit different. So how can one remove an app?
    • Visit Slack App Directory homepage.
    • Select Manage in the top right.
    • Select app from the list
    • If this is a third-party app (not created by your team), scroll down to the Remove Application section and select Remove App.
    • If some of your services are connected to this app (for example, BitBucket or Jira), click on the pencil icon and then on Remove in the top-right corner. If there is only one integration, you won't see the pencil icon – just click on Remove.

    How do I remove an integration?
    • Visit Slack App Directory homepage.
    • In the top-right corner, select Manage.
    • Select Custom Integrations in the list on the left.
    • Click on the integration you would like to remove.
    • Click the pencil icon next to this integration.
    • Click Remove in the top-right corner to remove the integration or click Disable to temporarily disable it.
    Voice and video messages on Slack
    Do you know that there is a simple way to send voice and video messages on Slack?

    Standuply bot enables you to send voice and video messages right inside Slack. It connects to YouTube via your Gmail account, creates a private channel and stores your messages there.

    You have full control over your messages. In addition, with your messages in a private video channel, it means nobody will see them unless you share the link.

    Then the bot shares a link on Slack which happens almost instantly. Here's how it works (once you add Standuply to your Slack team).
    Step #1. Run /voice or /video command in Slack
    Use corresponding slash commands in a channel or in DM where you want to post voice or video message.
    Step #2. Record a message in a browser
    Record a 5-minute voice or video message in a browser via a private link from Standuply.
    Step #3. The message is sent to Slack
    The recorded message is uploaded to YouTube, labeled as private, and the link is shared in Slack.
    Here's a step-by-step explainer video of how this feature works.
    3 Ways of Using Voice and Video on Slack
    Without voice and video communication, you can't work effectively, especially if your team is distributed. Slack offers you many voice and video opportunities.
    Built-in Slack video and audio calls
    Slack also comes with built-in native video and audio calls. Slack calls are known for their uninterrupted high-quality sound and video connection.

    To call a particular person, you need to do the following:
    • Open a direct message with that person and click the phone icon at the top-right corner
    • Your call will start immediately and the person you're calling will receive a pop-up notification
    • You can also click the camera icon to start a video call
    Q: How do I share my screen during a Slack call?
    Displaying one's screen during a call is a handy way to show a presentation, graphics, or discuss a project design. To do this, simply start the call and then click on the Share your screen icon. Besides, you can allow other members to draw on your screen by simply clicking the pencil icon. Then they will be able to more clearly share their ideas, highlight the main point in their presentation or draw attention to some flaws.
    If your workspace is on a paid plan, you can call several members at once:
    • Click the plus icon in the top-right corner of your call window.
    • Start typing a member's name and select from the suggested options.
    • Invite a person to your call.
    Want to share a call? No sweat:
    • Click the Plus icon in the top-right corner of your call window
    • Click Share this call
    • Select a channel from the drop-down menu and click Share. Or, you can simply copy a call link by clicking on Copy link and post to the desired channel.
    If you need to call from a channel, then (available for paid plans):
    • Open the channel and click the phone icon in the top-right corner
    • Confirm you would like to start a call and click Start new call
    • If you like, you can give the call a name so that members in the channel can immediately understand what is being discussed
    • A call notification will appear in the channel and any member (up to 15 people) can join by simply clicking Join this call.
    • You can also click on the camera icon to start a video call
    Q: How do I make Clipboard Sharing during a Slack call?
    If a member is sharing their screen with you during a call, any text you copy to clipboard will be sent back over to that person's shared screen. This facilitates collaboration, but there are a number of security and privacy issues involved here:

    1. Anything you copy will be sent to the other person's clipboard, even if you did not paste the copied content on the shared screen.
    2. If the teammate sharing her screen has a clipboard management tool installed, the content you copy will be saved for later access.
    If your Slack workspace is on the Free plan, you can call only one member of your workspace. With a paid subscription, you can call several members, a group or even an entire channel at once.
    If the member you're calling is on DND status, she will receive a missed call notification once she enables notification.
    Don't forget to use @channel or @here to notify channel members before a call and to send a follow up.
    During a call, only one member can share her screen at a time. When the person is done presenting, the next person can start showing his own screen.

    If you have problems setting up screen sharing or calls, check out the Slack Help Center, for assistance.
    Source: Slack Technologies Inc., Help Center.
    Source: Slack Technologies Inc., Help Center.
    Source: Slack Technologies Inc., Help Center.
    Slack Apps for calls
    Despite the fact that you can make calls using Slack's native feature, there are many apps and integrations that allow making calls from Slack as well.

    Some of these apps include Appear.in, Daily.co, Join.me, and others. You can find them in the Voice & Video category in the Slack App Directory.

    Also, the Slack Help Center describes how to use the best (in Slack's opinion) apps for video and audio calls in Slack. This can also be useful when choosing a suitable app.
    Chapter 4
    Q: What is a Slack Channel?
    Slack Channel is the place for topic-centered discussions. Channels are somewhat similar to groups and communities in social networks: a Slack channel has a creator, purpose, rules, and members (including apps).

    Channels are built in Slack to unite team members around their goals and projects or departments. All Channels are displayed on the left of your screen.

    There are three types of channels:
    • Public Channels - channels open for everyone in the company
    • Private Channels - channels with limited access, not for everyone in the company
    • Shared Channels - channels connecting your Slack with another company's Slack.

    The most important channel and the first one you see after registration is #general. By default, this is the company's primary channel for a team-wide communication.

    Channel, Thread, Group: what's the difference?
    Slack Channels, Threads, and Groups are forms of group chats with various options. Let's explore them in more detail.
    Q: How to make a Slack channel private?
    To make a Slack channel private, open the channel you want to convert and make sure you are a member of this channel:
    • Click on the gear icon in the top right and select Additional options
    • Choose Change to a private channel
    • Click Convert to private to confirm

    Then slackbot will send a message to the channel to let the channel members know it has become private.

    Learn How to Create a Shared Channel and Channel Name Guidelines

    Admins can limit the number of members with the right to write in a channel.
    For Admin
    Unfortunately, you can convert a public channel to private, but not vice versa.
    Q: How to join a Slack Channel?
    To join a new Slack channel, click Channels on the left:

    • Browse or search channels
    • Click the channel you'd like to join, choose either to Join Channel or to See more details
    • The See more details section contains a list of members and the purpose of a channel
    • To join this channel click Join Channel or just press Enter.
    If you are a Guest, you can join a channel by invitation only, and in the channel list, you will only see those which you've been invited to.
    Q: How to leave a Slack Channel?
    If you don't want to be a part of a channel, you can leave it. In this case, this channel will disappear from your Channels list.

    To leave a channel, open it, select the gear icon and click Leave #channel name. Another way is to type the slash command /leave in the channel you want to leave.
    If you leave a private channel, its messages and files will no longer appear in the search results.
    A few more key insights:
    1. You can leave any channel except #general.
    2. Single-Channel Guests can't leave the only channel they were invited to.
    3. Multi-Channel Guests can leave private channels, but they cannot leave public ones until the Admin removes them.

    By the way, instead of leaving a channel, you can simply mute it (see below).
    Q: How to mute a Slack Channel?
    If you're a member of a channel, but don't want to receive notifications, you can mute it. In this case, disabled channels will never appear as unread (in bold) in the channel list, and you will no longer receive notifications, including @mentions in this channel.

    There are two ways to do this:
    1. Open a channel and click the gear icon to open the channel menu and then select Mute.
    2. Type the slash command /mute in the channel.

    After that, the channel will appear in gray in the channel list.
    To unmute a channel, type the exact same command again or simply click the crossed out bell icon next to the channel name.
    Q: How to add or delete a member from a Slack Channel?
    There are several ways to add a member to a Slack channel:

    1. Type the /invite @name command in the channel message box. No worries, no one will see it.
    2. Or you can send a #channel name to a person as a part of a direct message, and they can join the channel by clicking on it.
    3. The third way to join a channel is to click the gear icon, select Invite members to join and type the name of a person. Then click Invite or Enter.

    A person can be removed in much the same way, but it can be done by Admins only.

    1. Type the /remove @member name command in a channel.
    2. Or enter the channel, click Show Channel Details. In the Member list find the person you want to remove, click Remove from #channel and then Yes, remove them. Slackbot will inform the person that they have been removed from the channel.
    Q: How to create a Slack channel?
    Usually, all members of the team, except Guests, can create channels, unless this action is restricted by the Admin.

    To create a Slack channel, click the plus icon next to Channels above the channel list on the left. Then:
    • Use the toggle to decide whether your channel will be public or private.
    • Enter a channel name (up to 21 characters).
    • Add a brief description or purpose of the channel so your teammates could see what the channel is about.
    • You can invite members to your channel immediately or skip this step. To do this, click Select members to invite and either select from the drop-down list or start typing the names of your teammates and choose from the suggested options.

    When everything is ready, click Create channel. It's done.
    Source: Slack Technologies Inc., Help Center.
    Q: How to rename a channel in Slack?
    To rename a Slack channel name, open the channel you want to rename.
    • Click the gear icon to open the channel settings
    • Select Additional options
    • Then Rename this channel
    • Enter a new name and click Rename Channel.
    Remember that channels can't have the same names.
    Q: What to do with a channel that you no longer need?
    Slack lets you delete or archive channels. If you delete it, the entire message history will be lost with no chance to be restored.

    If a channel is archived, it won't be shown on the channel list but can be restored. Moreover, data from an archived channel will appear in the search results.

    Keep in mind that only Admins can delete channels, but any member of a team can archive it.
    Q: How do I delete a channel in Slack?
    To delete a Slack channel, open it and then:
    • Click the gear icon to open the channel settings
    • Select Additional options
    • Then Delete this channel
    • Click Yes and then Delete Channel.

    If you want to delete an archived channel (with an archive icon next to its name), then:
    • Click Channels (above the channel list) on the left
    • Then Show: All channels and select Archived channels
    • Choose the channel to delete
    • Click the gear icon and click Delete
    • Once again Yes, permanently delete this channel, and finally Delete Channel.
    By the way, files from a deleted channel never disappear and can be found here – my.slack.com/files. However, if Admins want to get rid of the files from a deleted channel, they can delete them in the general directory using the link above.
    For Admin
    Remember that only Admins and Workspace Owners can delete channels.
    Q: How to archive a Slack channel?
    To archive a Slack channel, click the gear icon to open the channel settings.
    • Select Additional options
    • Click Archive this channel.
    By the way, files from a deleted channel never disappear and can be found here – my.slack.com/files. However, if Admins want to get rid of the files from a deleted channel, they can delete them in the general directory using the link above.
    For Admin
    Slackbot will notify all channel members that the channel has been archived. Archived channel members will still be able to search messages and shared files and view message history.

    However, apps set for this channel will be deactivated.
    Q: How to unarchive a Slack channel?
    To unarchive a channel, click Channels (above the channel list) on the left.
    • Click Show: All channels and then click Archived channels in the drop-down menu.
    • Select a channel and then click the gear icon.
    • Next, select un-archive #channel name.
    Q: How to create an announcement-only channel?
    Admins can create read-only channels. If you are the Admin, then this tip could be useful. A read-only channel or announcement-only channel is where only Admins have permission to post messages, and other participants can only read them.

    Slack allows you to do this only with the #general channel if you're on Free, Standard or Plus plan.
    • In the upper left click on the workspace name
    • Select Administration, then Workspace settings
    • Click the Permissions
    • Next to Messaging, click Expand
    • Under People who can post to #general make your selection
    • Click Save.
    This option could be very useful for team-wide announcements. Only Admins and Workspace Owners can delete announcement-only channels.
    Q: What is a User Group in Slack?
    A user group is an easy way to get the attention of several team members at once. When you mention a group of users in a chat, for example, @marketing, all marketers of this group will receive a notification.

    Based on a user group you can form a channel with the same members.

    Overall, user groups is a paid feature. If you're on the Free plan, then, unfortunately, you can't use this feature.
    Here is how to create or edit a user group.
    Group communication on Slack
    Q: What is a Slack Group DM?
    It's like a direct message, but for several people. This is what you do if you want to chat with more than one person in a DM. This feature is available on the Free plan.

    You can be part of such a group if you are invited to it, or you can create it yourself, here's how:
    • Click the plus icon next to Direct Messages on the left
    • Type names of one or more people you want to text and click on them to select
    • Press Enter to create a group.
    You can send a DM to one person, or a group DM to up to 8 other people (that will be 9 in total, including you).
    All your recent direct messages and groups will be displayed on the left under Channels.
    To turn your Group into a Channel, tap this link.
    For Admin
    Q: How to add a person to a Group DM?
    To add a person to a Group DM, open the Group page and click on the 'i' icon at the very top and then:
    • Click the arrow to open the menu
    • Select Invite more people
    • Select manually or via search who you would like to add
    • Press Enter or Go.
    Q: How to remove someone from a Group DM on Slack?
    Unfortunately, this is not possible. You'll have to create a new group if you don't want a certain person to be there.
    Remember that one group's message history can't be transferred to another one, and you can't delete anyone's messages in the group except your own.
    Q: How to move a Group DM to a private channel?
    You can move Group DM to a private channel. It can be handy if you want to invite more than 9 people into the conversation. It can be done by users with permission to create private channels.
    • Open the group and click the gear icon at the top
    • Select Convert to private channel
    • Then Yes, continue
    • Next, enter a channel name
    • Click Convert to a private channel

    Slackbot will notify all group members that their group chat has been transformed into a channel.
    If you invite someone to a private channel, they will see the entire message history. Thus, the newcomer will be able to read what had been discussed before they entered the chat.
    Q: How to start a thread in Slack?
    A Slack thread is pretty much the same as threads in the comments on forums. If you want to respond to someone else's message in a channel, but don't want to interfere with the current discussion, use this feature.

    At heart, a thread is a channel in a channel. That is, you can write, attach files, basically do anything you would do in a channel, but your messages won't appear directly in a channel, but will remain inside the thread.

    Messages in threads remain tied to a channel and are part of it. Notifications about new messages in a thread will be sent only to the thread participants and to a person whose message triggered the discussion.
    A couple of tips:

    How to start a thread? Just click the Start a thread icon or mouse over someone else's answer and click View thread
    How to make a reply in a thread visible to the entire channel? Before sending a message to a thread, tick Also send to #channel name
    How to keep track of a thread if you didn't write anything there and aren't going to? Mouse over a message or file and click More actions and then Follow thread
    How to unfollow a thread? Same as above but opt to Unfollow.

    Folks, use threads more actively. Your teammates will appreciate it.
    Q: How to change or delete messages from Slack?
    If you made a mistake, don't worry – there are two easy ways to edit messages in Slack:
    • Mouse over the message you want to edit and select More actions, then Edit message.
    • Or press the Up Arrow key on your keyboard and your last message will become editable.

    If you want to delete a message, the algorithm is quite similar:
    • Mouse over the message you want to edit and click More actionsDelete message.
    • Or, press the Up Arrow key on your keyboard, delete the text, press Enter, then Delete.
    A quick guide to Slack Messaging
    Q: Can teammates see the message that I deleted?
    No, they won't see it directly in Slack, but if you mention a person or use group mentions, then your teammates can get a notification by mail, and this is the only place where they can see it. The same holds true for mobile notifications.
    Q: Someone has deleted a message in Slack. Being the Admin, can I find out who did it?
    In Slack, a message can be deleted either by a person who wrote it or by Admins. Workspace owners and Admins can disable the message deletion feature altogether. Thus, no one else would be able to delete messages.
    Admins can remove any message from public or private channels and threads they are members of.
    For Admin
    Q: How to make a message unread?
    If you have already read an important message in a channel, but want to return to it later, you can mark it as Unread and here's how:
    • Mouse over the message you want to mark as unread
    • Click More actions
    • Then Mark unread.

    Now this message and others below will be marked as unread. In this case, you will see a marker for unread messages next to the channel name on the left and you can return to it later.