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Background on Terrible Mushroom and Write 500 Words.
Fact sheet
- Company: Terrible Mushroom Ltd
- Based in: United Kingdom
- First product: Write 500 Words, a Mac app that helps authors finish their books
- Business model: One-time purchase of £19.99 through the Mac App Store, after a 14-day free trial. No subscription, no account.
- Platform: macOS 26 Tahoe or later
- Release: 2026
- Company number: 17127662 (England and Wales)
- Registered office: 82A James Carter Road, Mildenhall, Suffolk, IP28 7DE
About Terrible Mushroom
Terrible Mushroom is an independent UK software studio. The studio makes Mac software that is paid for once rather than rented. No subscriptions, no accounts to sign up for. Its first product is Write 500 Words, a Mac app that helps authors finish their books.
About Write 500 Words
Write 500 Words is a Mac app that helps authors finish their books. It is built around a daily writing habit: a word target each day (five hundred by default, or a number the writer sets) that turns steady, modest progress into a finished draft. The manuscript and the notes around it stay in one place. The file format is plain markdown, so a finished book stays readable in any text editor, with no proprietary format. Write 500 Words is a one-time purchase of £19.99 on the Mac App Store and requires macOS 26 Tahoe or later.