Software Alternatives, Accelerators & Startups

f.lux VS ForthWrite

Compare f.lux VS ForthWrite and see what are their differences

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f.lux logo f.lux

f. lux is a piece of software for Windows, Mac, Linux, iOS, and Android that provides a blue light filter over your screen. Research suggests limiting our exposure to blue light in the hours before bedtime can help us fall asleep faster.

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
  • f.lux Landing page
    Landing page //
    2021-09-18
  • 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.

f.lux

Pricing URL
-
$ Details
-
Platforms
-
Release Date
-
Startup details
Country
United States

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

f.lux features and specs

  • Reduced Eye Strain
    f.lux adjusts the color temperature of your screen to match the lighting conditions, which can help reduce eye strain, especially during nighttime use.
  • Improved Sleep Quality
    By reducing blue light exposure in the evening, f.lux can help regulate your circadian rhythm, potentially improving sleep quality.
  • Customizable Settings
    f.lux offers various customization options allowing users to set their own schedules and adjust the color temperature to their preference.
  • Cross-Platform Availability
    f.lux is available on Windows, Mac, Linux, and iOS, making it accessible to a broad range of users regardless of their preferred platform.
  • Free to Use
    f.lux is available for free, making it an attractive option for users looking for screen color adjustment software without incurring costs.

Possible disadvantages of f.lux

  • Compatibility Issues
    Some applications and games may not function properly when f.lux is running, causing issues such as color inaccuracies or screen flickering.
  • Learning Curve
    While f.lux is relatively simple, new users may need some time to fully understand and effectively use its various settings and features.
  • Performance Impact
    On lower-end systems, running f.lux can sometimes lead to a minor performance impact, potentially slowing down the computer.
  • Limited Mobile Support
    f.lux is not available on Android devices, restricting its usage for users who primarily rely on this operating system.
  • Privacy Concerns
    As with any software that alters system settings, some users may have concerns about the level of access and control f.lux requires to function correctly.

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 f.lux

Overall verdict

  • f.lux is generally considered a good tool for those looking to reduce blue light exposure and improve their screen viewing experience, particularly at night. It is user-friendly and offers customizable settings to suit individual preferences.

Why this product is good

  • f.lux is designed to help reduce eye strain from computer screens by adjusting the color temperature according to the time of day, making it warmer at night to reduce blue light exposure. This can improve sleep quality and reduce fatigue for users who spend long hours in front of screens.

Recommended for

    f.lux is recommended for individuals who work late into the night on computers, people sensitive to blue light exposure, and anyone looking to improve their sleep patterns by minimizing screen glare after sunset.

Analysis of ForthWrite

Overall verdict

  • I don't have verified information about a product called ForthWrite (forthwrite.ai). I cannot confirm its features, quality, or reputation, so I'm unable to provide an accurate assessment of whether it's good.

Why this product is good

  • No reliable data available on this specific product in my knowledge base
  • This may be a newer product, a niche tool, or possibly a fictional/hypothetical name
  • Providing details without verified information could result in inaccurate or fabricated claims

Recommended for

  • Unable to determine without verified product information
  • Consider checking the official website, user reviews on platforms like G2 or Trustpilot, and independent tech review sites for accurate details

f.lux videos

F.lux Review - Should You Really Use It? [MY EXPERIENCE]

More videos:

  • Review - Does F.lux (FLUX) Really Work? Blue Light Filter test W/ Ghetto Science Applied.
  • Demo - F.lux - Review & Demo

ForthWrite videos

No ForthWrite videos yet. You could help us improve this page by suggesting one.

Add video

Category Popularity

0-100% (relative to f.lux and ForthWrite)
Work Management
100 100%
0% 0
Writing Tools
0 0%
100% 100
Color Temperature Adjuster
Email
0 0%
100% 100

Questions & Answers

As answered by people managing f.lux 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 f.lux and ForthWrite

f.lux Reviews

We have no reviews of f.lux 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, f.lux seems to be more popular. It has been mentiond 350 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.

f.lux mentions (350)

  • Adafruit Receives Demand Letter from Fenwick Legal Counsel on Behalf of Flux.ai
    Nor f.lux, the warm light software that got Sherlocked by every major OS. https://justgetflux.com/. - Source: Hacker News / about 1 month ago
  • Show HN: Monchromate โ€“ the best greyscale browser extension
    Somewhat related: I really like f.lux's "Darkroom" feature. Although I no longer use the app to reduce blue light after the advent of macOS's Night Shift, Darkroom mode tints the screen completely red (like a red version of Color Filters). It's great for working during the wee hours. https://justgetflux.com/. - Source: Hacker News / 12 months ago
  • Flux is fast and it's open source
    I know naming things is hard, but... https://justgetflux.com/ https://flux11pro.com/ (Maybe the same thing? Unclear.) https://github.com/flux-framework/flux-core (apparently archived now, but this was the first thing I thought of) https://www.flux.ai/ https://fluxcd.io/ https://runonflux.io/ https://fluxml.ai/. - Source: Hacker News / over 1 year ago
  • Modos Paper Monitor Pre-Launch on Crowd Supply
    Give Flux a try. https://justgetflux.com/ It did it before night mode and does it far better. ;). - Source: Hacker News / about 2 years ago
  • Tools that keep me productive
    For those evenings where I'm in front of the computer, f.lux is a must. Like some wise person said, "Be kind to your eyeballs". macOS's Nightshift kind of works, but f.lux destroys it. - Source: dev.to / about 2 years ago
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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 f.lux and ForthWrite, you can also consider the following products

LightBulb - Background application that adjusts screen gamma, making the colors appear warmer at night...

Superhuman - Superhuman is an email management tool.

Red Moon - Screen filter for night time phone use.

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.

Dimmer - A very small and free utility for Windows to reduce brightness on LCD/TFT screens.

Lavender - Realtime coaching for sales emails.