I built a Mac app that converts files when you rename them

Name: I built a Mac app that converts files when you rename them
Availability: InStock
Author: imfavourite

by imfavourite·Mar 11, 2026·2 points·3 comments

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AI Analysis

●●●BangerSlickCozy

Rename .mov to .mp3 or add _nobg to instantly convert without opening separate apps.

Strengths

•File system listener triggers conversions instantly without manual app switching or uploads.
•Taps native macOS APIs for Live Text and subject detection locally.
•Lifetime license avoids subscription fatigue common with similar conversion SaaS tools.

Weaknesses

•macOS only limits audience compared to cross-platform web converters or CLI.
•Power users might prefer Hazel or Shortcuts for customizable file automation workflows.

Post Description

Hi HN,

I built Morpholder after repeatedly running into the same annoying workflow on macOS.

Every time I needed to convert a file I had to open a converter, upload the file, download it again, and move it back to Finder. It always felt unnecessary when I already knew the format I needed.

So I tried a different idea: what if renaming the file actually converted it?

Morpholder watches folders and performs the real conversion when the extension changes.

For example:

favicon.png → favicon.ico photo.heic → photo.jpg video.mov → video.gif video.mp4 → audio.mp3

But it also unlocks some workflows beyond simple conversions:

- Append _nobg to an image → background is removed automatically (uses Apple’s subject detection) - Rename an image to .txt → text is extracted from the image using Live Text - Append _min → compress image for the web while preserving quality - Rename an image to .icns → builds a macOS app icon package - Append _pages to a PDF → exports each page as high-resolution images

The app runs in the menu bar and processes everything locally.

Curious what the HN community thinks — especially if you have ideas for other suffix-based workflows.

https://morpholder.com