Slack review: Free your business comms

Slack burst on the scene as the start-up darling of tech communication, and it remains one of the most popular options for businesses of all sizes. That's largely because of a very capable free tier, primarily limited by your access to older messages and advanced user management features.

Free workspaces give you search access to your team's 10,000 latest messages - although Slack saves your full message history just in case you do feel like ponying up for a paid plan in future. Also supported are up to 10 integrations with external apps or services, two-factor authentication for your users, a total 5GB of accessible storage and one-to-one voice and video calls.

The Standard tier gives you unlimited search and extensions, lets you invite guests from outside your organisation with access to specific channels, supports 15-person voice and video calls with interactive screen sharing, OAuth login, 10GB storage per user and access to priority support.

Bigger firms may wish to step up to the Plus tier, which adds SAML single-sign-on, Active Directory syncing, a 99.99% uptime guarantee and admin-level user provisioning and deprovisioning to help manage staff accounts. At this tier, you can also export group chat messages in JSON format, either as a one-off or on a regular schedule. Finally - and only available at bespoke pricing - is Slack Enterprise Grid, providing interconnected workspaces for even the biggest corporations.

Slack's fully functional free tier means that you can use it indefinitely - an option that many businesses take. However, if your business needs to full search access to records of staff communications, using a paid-for tier is strongly recommended.

Slack review: Functionality

Slack - like gamer and developer favourite Discord and open source rival Mattermost - takes more than a few cues from old-school IRC (Internet Relay Chat), with channels, /emotes, bots and easy one-to-one chat. Slack even once supported the open IRC and XMPP chat protocols, before dropping them in 2018. But what it lacks in open protocols, Slack makes up for in searchability, extensibility and multimedia features.

Clients are available for Windows, Linux, macOS, iOS and Android, alongside a fully featured web interface. Consistency of behaviour and interface between platforms is near-perfect, although there are a few features that only appear on limited platforms. The most conspicuous of these is dark mode, which only the mobile apps currently benefit from.

On joining, users are invited to set up a profile and are then dropped into your Slack workspace's #general channel - or any other channels you've set as default. A large chat pane allows everyone to talk amongst themselves, using Twitter-style @ mentions to get one another's attention as needed, including an @here option to notify everyone in a channel. You can also set up group tags, allowing you to @mention a pre-selected subset of users with a single tag. App notifications also appear if someone @s you in a group channel or sends you a direct message.

On the left, a sidebar shows all the channels you're a member of, threads - replies to a specific group chat message - that you're participating in, and any members you're having direct message chats with. At the top, you'll see the name of your workspace alongside a pulldown that gives you access to your user preferences and online status. At the bottom, you'll see options to add apps or connect any third-party integrations that have been configured for the workspace.

Slack has had integrated voice and video calling since 2016 (depending on your platform), with one-to-one calls available to all tiers and group VoIP and video chats of up to 15 people for paying users, complete with interactive screen sharing features.

If you're a member of more than one Slack workspace - for example if you have several businesses or teams with their own Slack accounts - then these can be displayed down a pane at the far left for ease of switching.

At the top right, a search box makes it easy to trawl through your current workspace's available message history, users and channels. This becomes a lot more useful on Slack's paid tiers, as even a dozen users can rapidly generate 10,000 messages.

Slack review: Configuration

Creating a new Slack workspace is just a matter of visiting a website, entering the email address you want to administrate it from, and coming up with a name.

While Slack has a wealth of dedicated chat apps, all configuration tasks, whether of your personal account or your workspaces, has to be done via a web browser. Here, you can do everything from setting and resetting your workspace's name, URL and icon to managing your members' status and admin privileges, creating user groups, viewing analytics and adding custom apps and integrations.

The admin interface feels rather busy and you may find that you do a lot of scrolling and tab-switching to find everything until you know where all the options are - we'd have appreciated an integrated search function. However, Slack is extremely well documented, which takes a lot of the pain out of finding the setting you're looking for.

Security options include enforced two-factor authentication for all workspace users, configurable session settings and, depending on your subscription, single sign-on via Google or your preferred SAML 2.0 platform, such as Microsoft Azure. If you suspect an admin account has been compromised, you can also force everyone to create new passwords.

You can invite colleagues - and guests if your subscription tier supports it - via both the web interface and stand-alone clients, but you'll need the web admin console to grant them roles, set their permissions and configure which settings - such as inviting others and adding to the channel's custom emoji selection - are available to users.

Slack review: Features, apps & integrations

Slack is decidedly feature rich, with a workspace bot that you can configure to provide automatic help and reminders to your users, seamless file sharing and fully certified security features - note, though, that unlike Microsoft, Slack doesn't have dedicated European or UK data centres and that your saved data can be stored in the US, subject to the EU/US Privacy Shield data protection framework.

Slack's Standard and Plus tiers introduce a number of extra features, such as interactive screen sharing and group voice and video chats, while enterprise users can manage multiple workspaces across large corporate structures, with corresponding levels of security and storage.

One of the most important points in favour of Slack across all tiers is that it provides support for a wide range of third-party apps and services. These include business tools such as Zendesk support tickets, GitHub repository updates, Trello projects, Google and Outlook calendars, Google Doc importing and a range of video and voice conferencing tools.

You'll also find some more frivolous options, such as animated gif insertions, polls, Twitter previews, lunch planning, music sharing and simple games. Slack's App Directory currently includes over 1,500 extensions and integrations and it's largely this broad compatibility that sets it apart from most of its online communications rivals.

And if your needs aren't catered to, there's an API that allows your business to create its own extensions as needed.

Slack review: Verdict

Slack's glossy and neatly packaged features have been massively influential across the unified communications industry, with apps from Discord to Microsoft Teams taking inspiration from elements of Slack's style. It's a fantastic tool for rich communications, but especially for text chat, with a free tier that's functional enough to fulfil the needs of many businesses and thorough record-keeping in paid tiers that's ideal if you need a solid communications audit trail.

There's support for screen sharing, voice and video calling, with both modest integrated features and extensions that give you access to more sophisticated third-party services such as Zoom, Skype and Cisco Webex. However, this isn't as well developed as Microsoft Teams' fully-featured Office 365-based VoIP telephony plans, so that's a better option if your communications needs require a full phone system.

However, Slack's extensibility and rich features mean that it's certainly the best free business chat and communications service for most SMBs, although open source shops and anyone who'd rather control their own online services could investigate self-hosting rival Mattermost.

Unfortunately, Slack's paid-for tiers are costly compared to almost all its rivals - it costs more than an Office 365 subscription including Teams, or a G Suite subscription including Hangouts. That makes it hard to justify a Slack subscription for most businesses unless you're already wedded to the free tier and really need access to your archives, more extensions, or a handful of other paid features.