Bethaniel is a private copy editor that runs on your own machine. No subscriptions, no trial periods, nothing uploaded unless you ask for it. Just you and your words. Free for indie authors, personal use, and small business.
Got an Intel Mac? Download for Intel instead.
Got a Mac with Apple Silicon? Download for Apple Silicon instead.
Current version:
Why Betty
A private copy editor on your machine
I built Betty to do the job I wanted from a copy editor.
Free and private
Betty runs fully on your own machine — no login, no internet, no account, no subscription. Free for personal use and small businesses. You can optionally hand the heavy lifting to an energy-optimised, fully private cloud in France, which keeps no copy of your writing, temporary or otherwise.
The editor you wished you had
For the pass before you send to a publishing house, or before you self-publish. Betty reads prose the way an editor does: she catches the usual grammar gremlins, and she notices when a sentence is doing too much work, or not enough.
Measured, not claimed
Betty surfaces 91% of mistakes, excluding commas and gets the right fix for 93% of them. The benchmark is public, including what she does badly. See the numbers →
You stay in the loop
Betty suggests — she never overwrites. Every correction waits for your yes, and the ones she is unsure of arrive marked as unsure.
About one kettle.
Editing a 60,000-word novel uses roughly the electricity it takes to boil a kettle.* The bigger saving is the hours: the same pass by hand is twenty to forty at a desk. You still read every suggestion — but in about one. * Estimated, not measured: about 643,000 tokens for a 60,000-word copy edit, at published energy-per-token figures. Translation is the exception: it runs on a far larger model in a data centre, and is not one kettle.
Getting started
Four steps. Then just write.
Download
Grab the installer for your system above. It's one file — no package manager, no dependencies to chase down.
Install
Open the installer and follow along. First thing you have to do, once Betty is installed, is select the size of Betty you think your machine can handle. Don't worry, you can always change your mind later.
Open your writing
Add your manuscript and a description of the style you're aiming for. Betty works with plain text, Markdown, and most common document formats. With the style document, you can give custom instructions such as "Don't correct the pirates. They are supposed to talk like that."
Let her read
Hit Start Job and Betty will go through your work. Suggestions come up for you to evaluate — accept them, ignore them, your choice.
Measured
Numbers, not adjectives.
Every figure here comes from a benchmark you can re-run from the repository — errors planted at known places in four languages, then counted. Including the one we do badly on.
of the obvious mistakes surfaced — misspellings, doubled words, wrong words, wrong capitals, wrong dialect, missing punctuation. Betty suggests the right fix for 93% of those.
commas. That is the honest number, it is the largest hole in the product, and you should plan a human pass if commas matter to you.
For teams
Betty means Business.
Running a publishing house or a team of writers, editors, or translators? Betty can do quite a bit more when she has a proper desk to work at.
That might mean a dedicated machine tucked in your office, or a workstation in the cloud — whichever fits your setup. Either way, your team gets real power and your documents go nowhere they shouldn't.
Drop me a note and I'll figure out what makes sense for you. (See the license & rights of use for details on when a commercial license is required.)
A few notes
What Betty is — and isn't.
I think Betty is good. I also think it's important to be clear about where she helps, where she doesn't, and what you're signing up for.
Read the full disclosure
Betty is a tool, not a professional. She is a writing aid — not a qualified copy editor, proofreader, or legal reviewer. Her suggestions are starting points, not verdicts. The final call on every sentence is yours.
She will sometimes be wrong. Language is context-dependent in ways that are genuinely hard. Betty will occasionally flag something that was fine, miss something that wasn’t, or suggest a change that makes things worse. Treat her output as a second opinion, not a final edit.
Nothing leaves your machine. Betty processes text entirely on your own hardware. No part of what you write is sent to any server, stored in any cloud, shared with any third party, or used to train anything. The text you put in stays in. Period.
Betty requires capable hardware. She needs at least 8 GB of RAM and approximately 3 GB of free disk space. On older or lower-spec machines she may run slowly or not at all. She does real computational work — there is no lightweight version.
Supported platforms. Betty is currently available for macOS 12 or later, Windows 10 (64-bit) or later, and Linux systems running glibc 2.31 or newer. Other platforms are not supported at this time.
Betty is free, and intends to stay that way. Running Betty on your own machine has no usage limit, no subscription and no trial period, and that is the product. There is one paid option — a cloud service, charged per job, for machines that cannot run a model locally — and it is never required to use Betty. If anything about the free version changes, it will be announced here before it takes effect, with enough notice to make a considered decision.
No warranties. Betty is provided as-is. I make no guarantees about accuracy, fitness for any particular purpose, or uninterrupted availability. Use her at your own discretion.
Stay in the loop
Notes from Betty.
Stay in the loop with Betty's updates — all cozy and nice stuff, I swear. Since we don't ask you to sign in or in any way associate you with an email address, this is the only way I'll be able to reach you with news, updates, and announcements. I promise not to spam you — and you can unsubscribe at any time.
Betty is free
But coffee isn't.
"If Betty saved you an afternoon of re-reading your own prose in mounting despair, and you want to help me keep building her, buy the team a coffee. It genuinely helps keep the lights on."
Buy the team a coffeeAbout the team
Hi, I am the team!
My name is Simon — I have a Ph.D. in Data Science, and a bunch of experience in software development by now. But let's skip the boring stuff…
I am also the author of the Worldsea Trilogy which you can (and totally should) go buy right now.. I love writing stories but I hate fixing typos. That's why I created Betty — so that more stories can come to life, even the ones that do not have the financial backing to hire professional editors.
System requirements
What you'll need.
| Platform | Minimum version | Notes |
|---|---|---|
| macOS | 12 Monterey or later | Apple Silicon & Intel both supported |
| Windows | Windows 10 (64-bit) or later | |
| Linux | glibc 2.31 or newer | Debian 11, Ubuntu 20.04, or equivalent |
| Also required: 8 GB RAM minimum · approx. 3 GB free disk space | ||
License & rights of use
License & rights of use.
Bethaniel is provided under a custom source-available license. Please read the terms below carefully.
Free use
You may use Bethaniel free of charge if you meet all of the following conditions:
- Personal / non-commercial use — any individual using Bethaniel for their own manuscripts, hobby projects, or personal editing needs; OR
-
Small-business commercial use — a company, team,
or sole trader where:
- The organization has fewer than 5 employees, contractors, consultants, or regular users; AND
- The organization's annual gross revenue is less than USD $1,000,000.
Commercial license required
If your organization does not meet both of the criteria above (i.e. 5+ people or ≥ $1 M revenue), you must obtain a commercial license before using Bethaniel. Please reach out via the contact form and I'll get you sorted.
Restrictions
Regardless of whether you qualify for free use:
- No redistribution — You may not redistribute, sublicense, sell, or share the Bethaniel source code or compiled binaries to third parties.
- No modification — You may not fork, modify, adapt, or create derivative works of Bethaniel for your own commercial product or service without prior written permission.
- No reverse engineering of prompts — The prompt engineering, system prompts, and editing logic are proprietary. You may not extract them for use in other products.
Attribution
Attribution is encouraged but not required. If Bethaniel helped you ship your book or edit your manuscript, a mention is always appreciated — but you're under no obligation.
No warranty
Bethaniel is provided "AS IS", without warranty of any kind, express or implied. The author(s) are not liable for any damages arising from the use of this software.
Model licenses
Models used in Bethaniel are Apache 2.0 licensed. For more details, see: github.com/SimonGrund/bethaniel/blob/main/MODEL_LICENSES.md
© 2025–2026 Bethaniel. All rights reserved.