Software Alternatives, Accelerators & Startups

Caldis MOS VS ForthWrite

Compare Caldis MOS VS ForthWrite and see what are their differences

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Caldis MOS logo Caldis MOS

A little job for your mouse.

ForthWrite logo ForthWrite

Email that sounds like you, and gets measurably more like you every week. Drafts in Gmail, Outlook, and the browser. Free to start.
Visit Website
  • Caldis MOS Landing page
    Landing page //
    2019-09-12
  • ForthWrite Landing Page
    Landing Page //
    2026-06-19
  • ForthWrite Dashboard
    Dashboard //
    2026-06-19
  • ForthWrite In Gmail
    In Gmail //
    2026-06-19
  • ForthWrite Pricing
    Pricing //
    2026-06-19

ForthWrite is an AI email writing assistant for Gmail and Outlook that learns your writing style from your real sent mail. The more you use it, the more it sounds like you. Get smart drafts in seconds, auto-draft replies before you open your inbox, and maintain your personal voice at scale. Free to start, no credit card required. Works inside Gmail and Outlook on the web.

How it works

ForthWrite captures your tone, sentence rhythm, and sign-offs from your actual sent emails, then uses that profile to generate drafts that match how you write, not a generic AI voice. Every draft you edit or send improves the model over time.

Key features

  • Auto-draft: replies waiting in Gmail before you open your inbox
  • Voice matching from your real sent mail, not templates
  • Recipient-aware drafts that adapt to who you are emailing
  • Prompt Lab for version-controlling and A/B testing your persona prompt
  • BYOK support: bring your own API key for Claude, OpenAI, Grok, Mistral, and more
  • Works in Gmail and Outlook on the web, plus a standalone browser widget
  • Training data export and full data portability

Who uses it

Professionals who send high volumes of relationship-critical email: lawyers, financial advisors, recruiters, account executives, founders, and anyone who wants their inbox handled without sounding like a chatbot wrote it.

Pricing

Free tier includes 10 drafts per week with no credit card required. Paid plans start at $12/month and include unlimited drafts, custom persona prompts, and auto-draft.

Caldis MOS

Pricing URL
-
$ Details
Platforms
-
Release Date
-
Startup details
Country
China

ForthWrite

$ Details
freemium $12.0 / Monthly (Standard plan)
Platforms
Web
Release Date
2026 June
Startup details
Country
United States
State
California
City
San Diego
Founder(s)
Curtis Boortz
Employees
1 - 9

Caldis MOS features and specs

  • Customizable
    Caldis MOS offers flexibility in configuration, allowing users to customize mouse behaviors to suit their specific needs.
  • Cross-Platform
    Caldis MOS supports multiple operating systems, making it a versatile solution for users with different setups.
  • Open Source
    Being open source, Caldis MOS allows developers to inspect, modify, and contribute to the code, fostering a community-driven development.
  • Enhanced Productivity
    By enabling complex mouse gestures and macros, Caldis MOS can significantly boost user productivity.
  • Frequent Updates
    The software receives regular updates, ensuring that it remains secure and packed with the latest features.

Possible disadvantages of Caldis MOS

  • Learning Curve
    New users might find the customization options and settings overwhelming, requiring a period of adjustment and learning.
  • Potential Instability
    As an advanced tool that interacts deeply with the mouse hardware and software, there might be occasional stability issues or bugs.
  • Resource Intensive
    Caldis MOS can be resource-intensive, potentially impacting system performance, especially on older or less powerful machines.
  • Limited Support
    Being a community-driven project, users might find support options limited compared to commercial software.
  • Compatibility Issues
    There may be compatibility issues with certain devices or software, necessitating troubleshooting and potential workaround solutions.

ForthWrite features and specs

  • Voice Matching
    Learns from your real sent mail, not templates
  • Auto-draft replies
    Replies waiting in Gmail before you open your inbox
  • Batch-drafting
    Draft replies for your entire inbox with one click
  • Works in browser
    Gmail, Outlook, and web browsers
  • BYOK support
    Claude, OpenAI, Grok, Mistral, and more
  • Prompt Lab
    Version control and A/B test your persona prompt
  • Free tier
    10 drafts per week, no credit card required

Analysis of Caldis MOS

Overall verdict

  • Yes, Caldis MOS is considered a good tool for users who need enhanced control over their mouse functionality without the overhead of more complex software.

Why this product is good

  • Caldis MOS (mos.caldis.me) is appreciated for its lightweight design and effective functionality for managing mouse interactions. It is easy to configure and doesn't consume significant system resources, making it optimal for users looking for a minimalist yet powerful mouse control solution.

Recommended for

    People who frequently switch between multiple input devices or require precise mouse control for tasks like gaming, design work, or productivity applications might find Caldis MOS particularly beneficial.

Category Popularity

0-100% (relative to Caldis MOS and ForthWrite)
Note Taking
100 100%
0% 0
Writing Tools
0 0%
100% 100
Game Reviews
100 100%
0% 0
Email
0 0%
100% 100

Questions & Answers

As answered by people managing Caldis MOS and ForthWrite.

Which are the primary technologies used for building your product?

ForthWrite's answer:

Next.js, React, Supabase, Anthropic Claude, OpenAI, Stripe, Vercel, Chrome Extensions API

What makes your product unique?

ForthWrite's answer:

ForthWrite learns your writing style from your actual sent mail, not a generic prompt. Every draft sounds like you wrote it because it was trained on how you actually write. It also auto-drafts replies before you open your inbox, so your email is partially handled before your day starts.

Why should a person choose your product over its competitors?

ForthWrite's answer:

Most AI email tools give you a blank box and a "write for me" button. ForthWrite builds a voice profile from your sent history and gets more accurate with every draft you edit or send. Unlike ChatGPT or Gemini, it works natively inside Gmail and Outlook with no copy-paste. Unlike Lavender, it writes the draft, not just scores it.

How would you describe the primary audience of your product?

ForthWrite's answer:

Professionals who send high volumes of relationship-critical email and cannot afford to sound generic: lawyers, financial advisors, recruiters, account executives, consultants, and founders managing their own inbox.

What's the story behind your product?

ForthWrite's answer:

Built out of frustration with AI writing tools that produce text that sounds nothing like the person sending it, and as a way to handle large amounts of daily email. The core insight was that your sent mail is the best training data you already have, and no tool was using it.

User comments

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Reviews

These are some of the external sources and on-site user reviews we've used to compare Caldis MOS and ForthWrite

Caldis MOS Reviews

We have no reviews of Caldis MOS yet.
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ForthWrite Reviews

  1. curtisboortz
    ยท Founder at ForthWrite ยท
    I built ForthWrite to fix generic AI email, and I still use it every day

    I built ForthWrite because I kept sending emails that sounded like they came from the same generic AI as everyone else. After launching it, I still use it for my own inbox every day, which is about the most honest endorsement I can give.

    The Chrome extension lives inside Gmail and Outlook on the web. Open a thread, hit Alt+Shift+D, and a draft comes back in your voice, not a template. The free tier is real: 10 drafts per week, no API key, no credit card. Voice matching is included on free, because that is the point.

    What keeps it useful compared to Gemini or a chat tab: it learns from what you actually send. Every edit you make before hitting send becomes a signal. Over time the drafts drift closer to how you really write, and the dashboard shows the improvement curve so you can see it happening.

    The web compose surface lets you draft from forthwrite.ai without installing anything, useful for people who want to try before committing to the extension.

    Standard adds recipient-aware and intent-aware drafting plus AI coaching. Pro adds auto-draft (replies waiting when you open Gmail), batch replies, and Prompt Lab for version-controlling your prompts. Teams adds a shared persona and seat-level analytics.

    ForthWrite is not for everyone. If you just need quick replies and tone does not matter, Gemini is free and already in your inbox. ForthWrite is for people where tone does matter: client communication, relationship-driven threads, external correspondence where sounding off costs something real.

    Disclosure: I am the founder and use it daily. Happy to answer questions in the comments.

    ๐Ÿ Competitors: Jace.ai, Fyxer, Mailmeteor
    ๐Ÿ‘ Pros:    Drafts land inside gmail and outlook; no copy-pasting from a chat window|Voice matching is on the free tier, not paywalled behind paid plans|No api key, no credit card to start; free tier runs on a server-side proxy|Learns from every edit you make before sending; drafts improve over time|Full keyboard flow: alt+shift+d to draft in any thread, no mouse required|Byok on paid plans, 9 providers supported, keys encrypted at rest|Web compose at forthwrite.ai works without installing the extension at all
    ๐Ÿ‘Ž Cons:    10 free drafts/week is enough to evaluate, not enough for a heavy inbox|Auto-draft, batch replies, and prompt lab all require the pro tier|Early-stage product; fewer third-party integrations than mature inbox tools|No mobile app: the extension and add-in are desktop-only (chrome on web, or the outlook desktop add-in)

Social recommendations and mentions

Based on our record, Caldis MOS seems to be more popular. It has been mentiond 91 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.

Caldis MOS mentions (91)

  • Zed Editor Theme-Builder
    You could use Mos, which also has the advantage that smooth scrolling works the same in every app (speed, acceleration etc) https://mos.caldis.me/. - Source: Hacker News / about 2 months ago
  • Building the Mouse Logitech Won't Make
    I frequently came across this, but it doesn't work for iPadOS so I never tried it, maybe it would work for you: https://mos.caldis.me/. - Source: Hacker News / 11 months ago
  • Silicon Valley Tea Party a.k.a. the great 1998 Linux revolt take II
    Only with hardware acceleration turned off. Which in my experience causes a stuttery and laggy experience which can hardly be described as "smooth". If you really want to use MacOS's smooth scrolling, use MOS (https://mos.caldis.me) and get a beefy Mac because the base models will stutter like I mentioned. - Source: Hacker News / over 1 year ago
  • macOS Sequoia Preview
    There is also Mos, it is a bit smoother in my experience: https://mos.caldis.me/. - Source: Hacker News / about 2 years ago
  • Mac Mouse Fix: Do the things you do on a trackpad. Without a trackpad
    It looks like this competes with Mos.app[0]. Honestly, I'm not sure how folks use non-magic mice without this. [0]: https://mos.caldis.me. - Source: Hacker News / almost 3 years ago
View more

ForthWrite mentions (0)

We have not tracked any mentions of ForthWrite yet. Tracking of ForthWrite recommendations started around Jun 2026.

What are some alternatives?

When comparing Caldis MOS and ForthWrite, you can also consider the following products

Mac Mouse Fix - A simple way to make your 3rd party mouse better.

Superhuman - Superhuman is an email management tool.

Rectangle - Window management app based on Spectacle, written in Swift.

Gemini - Gemini, formerly known as Bard, is a generative artificial intelligence chatbot developed by Google. Based on the large language model (LLM) of the same name, it was launched in 2023 in response to the rise of OpenAI's ChatGPT.

LinearMouse - LinearMouse is a free and open-source utility for macOS which aims to improve the experience and functionality of third-party mice.

Lavender - Realtime coaching for sales emails.