What is the best free Slack alternative?

Pumble's free plan has unlimited users and unlimited message history, which is the main thing Slack's free plan lacks. Zulip's free cloud plan keeps 10,000 messages searchable, and Discord is free but built for communities rather than companies.

How long does Slack's free plan keep messages?

90 days. Older messages and files are hidden until you upgrade to a paid plan, which starts at $7.25 per user a month billed annually.

Is Opser cheaper than Slack?

For chat alone, no. Slack Pro for five people costs about $36 a month billed annually, while Opser Foundation is $99 a month for the business with five seats. Opser's price also covers apps like Customers, Helpdesk, and Tasks, plus monthly AI credits, so it costs less than Slack plus separate tools for those jobs.

Does Opser Chat have voice or video calls?

Not yet. Opser Chat covers channels, direct messages, threads, mentions, reactions, pins, saved messages, and file sharing. Teams that rely on Slack huddles keep a meeting tool such as Google Meet or Zoom alongside it.

Can an AI agent read our team chat in Opser?

Your agent works with your access, so it can read and search the channels and direct messages you're part of, catch you up on what you missed, and draft messages. By default, it asks for your approval before it posts anything.

The best Slack alternatives for startups in 2026: 6 compared

Opser, Microsoft Teams, Google Chat, Zulip, Pumble, and Discord compared on price, free plans, and fit, for startups outgrowing Slack or its per-seat bill.

Simone Zamparini

October 2, 20265 min read

Illustration of two rounded speech bubbles, a small stack of ceramic tiles, a paper card file, and a desk bell on an ivory platform.

Key takeaways

Startups usually leave Slack over the per-seat price as the team grows, the free plan's 90-day message history, or chat living apart from the rest of the work.
Slack Pro costs $7.25 per user a month billed annually, Business+ $15, and the free plan keeps 90 days of history.
The cheapest real alternatives are Pumble, free with unlimited history, and Zulip, from $6.67 a user. Google Chat and Microsoft Teams make sense if you already pay for Google Workspace or Microsoft 365.
Opser puts team chat in the same workspace as your customers, tasks, and AI agents, priced per business instead of per seat.
If all you need is chat, Opser isn't the cheapest pick. It pays off when it replaces chat plus a CRM, a help desk, and AI tools.

Most startups pick Slack on day one, and it's a good default. A year later, three things tend to push them to look around.

The first is the bill. Slack charges per person, so every hire adds to it, and the plan with Slack's advanced AI costs $15 per user a month billed annually. The second is the free plan's limit: it keeps 90 days of message history, so the decision you made in spring is gone by summer. The third is quieter. The conversation about a customer happens in Slack, while the customer record, the support ticket, and the task live in three other tools, and somebody has to copy things between them.

We build Opser, so we're biased. This comparison still tries to be fair: each alternative has a real reason to pick it, and for some teams that reason beats ours.

What should a startup look for in a Slack alternative?

Start with what you actually need, because team chat tools have converged on the basics. Channels, direct messages, threads, mentions, reactions, file sharing, and mobile apps are standard almost everywhere. The differences that matter for a small team are elsewhere:

Price as you grow. Per-seat pricing is cheap at three people and painful at thirty.
Free plan limits. Watch message history, integrations, and storage, since those are what free plans cap.
Where the work lives. Chat connected to your customers, tasks, and support saves the copying between tools.
AI that does work. Summaries are table stakes in 2026. An agent that can act on what's discussed is the newer question.
Calls and guests. If you live in huddles or talk with clients in shared channels, check those features first.

The 6 best Slack alternatives for startups at a glance

Tool	Price	Best for
Opser	Free for 2 seats, then from $49 a month per business	Chat, customers, support, and AI agents in one place
Microsoft Teams	$7 per user with Microsoft 365	Teams already on Microsoft 365
Google Chat	$7 per user with Google Workspace	Teams already on Google Workspace
Zulip	Free up to 10,000 searchable messages, then $6.67 per user	Topic threads and self-hosting
Pumble	Free with unlimited history, then $2.49 per user	The lowest price
Discord	Free	Communities and two-founder teams

Paid prices are per month, billed annually, from each vendor's pricing page in October 2026. For reference, Slack Pro is $7.25 per user a month billed annually ($8.75 monthly), and Business+ is $15 ($18 monthly).

Which Slack alternatives are worth a look?

1. Opser: chat in the same workspace as your customers and agents

Opser is a workspace for running a small business: apps like Customers, Helpdesk, Tasks, and Email, with an AI agent for every teammate. Chat is one of those apps. It has channels, direct messages, threads, mentions, reactions, read receipts, pins, saved messages, status, and file sharing, and it works in the browser and on your phone.

What makes it different is what sits around it. Your agent can read and search the conversations you're part of, so "catch me up on #sales" or "find what we decided about the pricing page" works across your channels. Because the agent also works in your other apps, the thread about a new lead can become a contact in Customers and a task with an owner, without anyone copying it over. When the agent writes in Chat for you, it asks before it posts by default.

Pricing is per business. The free plan covers two seats and three apps. Starter is $49 a month with three seats and ten apps, Foundation is $99 with five seats, and Accelerate is $199 with ten, each with monthly AI credits included. See the full plans.

Where it falls short today: there are no voice or video calls and no guest access for people outside your workspace, so huddle-heavy teams keep a meeting tool alongside it. If all you need is chat, it isn't the cheapest option on this list.

2. Microsoft Teams: the default if you're on Microsoft 365

Teams comes with Microsoft 365 Business Basic at $7 per user a month billed annually, together with Outlook, OneDrive, and the Office apps on the web. Meetings are its strength, with deep calendar and Office integration. The free version limits group meetings to 60 minutes. For a startup already paying for Microsoft 365, Teams costs nothing extra, which is hard to argue with.

3. Google Chat: the default if you're on Google Workspace

Google Chat is included in every Google Workspace plan, starting at $7 per user a month billed annually for Business Starter, and Gemini is included too. It's simpler than Slack, with spaces, threads, and tight links to Gmail, Drive, and Meet. Teams that live in Google Docs rarely need more, and there's no separate bill.

4. Zulip: topic-based threads, open source, and self-hostable

Zulip organizes every conversation into a channel and a topic, which keeps busy channels readable and makes old discussions easy to find. The cloud Standard plan is $6.67 per user a month billed annually ($8 monthly), and the free cloud plan keeps 10,000 messages searchable. It's open source and can be self-hosted, which matters to teams with strict data requirements.

5. Pumble: the cheapest drop-in replacement

Pumble looks and works a lot like Slack, and its free plan gives unlimited users and unlimited message history with 10 GB of storage in total. Paid plans start at $2.49 per user a month billed annually. If your only complaint about Slack is the price, Pumble is the most direct answer.

6. Discord: free, with great voice, built for communities

Plenty of very early teams run on Discord because it's free and its always-on voice channels are excellent. It was built for communities rather than companies, though, so admin controls, compliance features, and business integrations are thin. It works for a few founders, and most teams move off it once they hire.

Which Slack alternative should a startup choose?

You already pay for Microsoft 365 or Google Workspace: use Teams or Google Chat. You're paying for it anyway.
You want Slack for less money: try Pumble first, then Zulip if your channels get noisy.
You need self-hosting or open source: Zulip.
You're two founders on a budget: Discord or Pumble's free plan.
Your chat is mostly about customers, support, and getting work done: Opser, because the conversation, the records, and the agent that acts on them live in one place.

How do you switch from Slack without losing history?

Export your Slack workspace before you leave. Slack lets workspace owners export messages from public channels on every plan, and wider exports on its higher plans, so you keep a searchable archive of past decisions. Then move one team first, run both tools side by side for a week, and set a date after which Slack goes read-only. People follow the conversation, so the switch sticks once the important channels move.

If you're moving to Opser, start with the channels that are really about customers or support, since those gain the most from sitting next to Customers and Helpdesk.

Frequently asked questions

What is the best free Slack alternative?: Pumble's free plan has unlimited users and unlimited message history, which is the main thing Slack's free plan lacks. Zulip's free cloud plan keeps 10,000 messages searchable, and Discord is free but built for communities rather than companies.
How long does Slack's free plan keep messages?: 90 days. Older messages and files are hidden until you upgrade to a paid plan, which starts at $7.25 per user a month billed annually.
Is Opser cheaper than Slack?: For chat alone, no. Slack Pro for five people costs about $36 a month billed annually, while Opser Foundation is $99 a month for the business with five seats. Opser's price also covers apps like Customers, Helpdesk, and Tasks, plus monthly AI credits, so it costs less than Slack plus separate tools for those jobs.
Does Opser Chat have voice or video calls?: Not yet. Opser Chat covers channels, direct messages, threads, mentions, reactions, pins, saved messages, and file sharing. Teams that rely on Slack huddles keep a meeting tool such as Google Meet or Zoom alongside it.
Can an AI agent read our team chat in Opser?: Your agent works with your access, so it can read and search the channels and direct messages you're part of, catch you up on what you missed, and draft messages. By default, it asks for your approval before it posts anything.