
Slack
Rocket.Chat
Discord
Microsoft Teams
Element.io
Telegram
Zulip
Mattermost is an open source alternative to Slack.

NovoPsych
Digital Psychology assessments with research-backed UX for neurodivergent patients. Better completion rates, more comfortable patient experience, instant scoring, trend tracking with secured data hosting.

Which is more popular?
Based on our record, Mattermost seems to be more popular. It has been mentioned 76 times since March 2021.
Website, pricing, platforms and company facts side by side.
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| Website | mattermost.com | clientforms.app |
| Pricing | ||
| Company | Startup from the United States | — |
| Listed in |
What each product offers, as listed by its team.


Possible disadvantages
Possible disadvantages
An editorial look at what each product does well and who it suits.


Overall verdict
Why this product is good
Recommended for
Mattermost is recommended for organizations that prioritize data privacy and security, need extensive customization options, or are looking to integrate a collaboration tool into existing systems. It is also suitable for teams in regulated industries requiring on-premises solutions.
Overall verdict
Why this product is good
Recommended for
Walkthroughs and reviews on video.
Mattermost - An Open Source, Self Hosted, Slack Chat Alternative
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How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing Mattermost and ClientForms.app.
ClientForms.app's answer:
Frontend: Next.js 15 (React 19), Tailwind CSS Backend: Supabase (PostgreSQL, Row-Level Security) Authentication: Clerk Payments: Stripe Hosting: Vercel (Sydney region) Database hosting: Supabase (Australian data residency)
ClientForms.app's answer:
Psychologists who assess ADHD and autism. Typically private practice, solo or small group (1-5 clinicians), currently using paper forms and spending hours on admin per assessment. They want something that works and is secure.
ClientForms.app's answer:
Neurodivergent-first design. Most digital forms just replicate paper online. ClientForms is built specifically for ADHD and autism patients - progress bars with time remaining (helps with time blindness), softer colours instead of harsh white, sticky headers so you always know where you are. The forms are designed to reduce anxiety and improve completion rates.
ClientForms.app's answer:
Most clinical software treats patients as an afterthought. ClientForms is designed specifically for neurodivergent users who are filling out the forms, progress indicators, time estimates, calmer colours, predictable layouts. One link, no signup required, works on any device. Patients just open and complete.
Share your experience with using Mattermost and ClientForms.app. For example, how are they different and which one is better?
External articles and on-site reviews we used to compare the two products.


Mattermost is an open-source platform that enables safe collaboration in self-hosted chat programs featuring file sharing, search, and integrations; groups and businesses can use it as an internal chat.
Mattermost uses monolithic architecture, which is tightly coupled and complex to understand. It restricts the scalability of the collaboration tool, which is a limitation for growing businesses. In that case,...
Below is a curated list of the 12 best self-hosted messaging apps like MirrorFly, Mattermost, Zulio, Nextcloud, and Rocket.chat that offer unique collaboration features and lets you take full control of your data.
We have no reviews of ClientForms.app yet. Be the first one to post
Recommendations tracked on public social media and blogs since March 2021.


Mattermost | Remote (US and Canada) | FT | Multiple roles Mattermost (https://mattermost.com) is an open-core collaboration and workflow automation platform for air-gapped, on-prem and private clouds. Our customers are in defense,... - Source: Hacker News / about 1 month ago
The amazing thing is that there is almost always an open-source alternative that is 10x better in many ways, in the case of slack https://mattermost.com/ I'm looking forward for AI to make it very easy to deploy your own tools and walk... - Source: Hacker News / 3 months ago
How does it compare to MatterMost [1]? [1] https://mattermost.com/. - Source: Hacker News / 6 months ago
Tracking ClientForms.app since Dec 2025.
When comparing Mattermost and ClientForms.app, you can also consider the following products.

A messaging app for teams who see through the Earth!
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NovoPsych is a tool that is used for outcome monitoring via conducting psychological tests online.
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Rocket.Chat is a Web Chat Server, developed in JavaScript, using the Meteor fullstack framework.
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Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.
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Microsoft Teams provides the enterprise-level security, compliance and management features you expect from Office 365, including broad support for compliance standards, and eDiscovery and legal hold for channels, chats, and files.
Compare Microsoft Teams to Mattermost or ClientForms.app:

Secure messaging app with strong end-to-end encryption, advanced group chat privacy settings, secure video calls for teams, encrypted communication using Matrix open network. Riot.im is now Element.
Compare Element.io to Mattermost or ClientForms.app: