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Show HN: I built a Mac app that converts files when you rename them
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 https://morpholder.com
- merl1n 7mo agoPretty sleek! The fact that you have to manually add folders to watch destroys the magic a bit IMO. Would it be possible to just watch the whole user folder and what would be the performance implications? Also can it differentiate between a user renaming a file and a potential background job programmatically modifying files? I could imagine this leading to some weird results when multiple applications are "fighting" over the same file ...
- imfavourite 7mo agoThanks! Glad you like it. Regarding watching the whole user directory: surprisingly, performance isn't an issue at all. macOS handles file system events very efficiently, so watching ~/ wouldn't cause any noticeable overhead. The decision to make it manual is purely about security and user control. I wanted a strict "opt-in" approach so users know exactly where the app is operating, preventing any unexpected accidental conversions in sensitive folders. It's all about the principle of least surprise. As for background jobs vs. manual renaming: Morpholder is designed to be highly specific. It only triggers when a file is renamed to a supported target extension (e.g., specifically to .jpg or .mp3) or when one of the exact keywords (like _nobg or _min) is appended. Because the trigger conditions are so narrow, the chances of conflicting with a random background script are very low. That being said, you bring up a really good point about edge cases with file locking and multiple apps interacting simultaneously. I'll definitely run some additional stress tests on those scenarios. Really appreciate the feedback and food for thought!
- imfavourite 7mo agoMorpholder updated: New: Added support for converting SVG to any raster format New: Added support for vectorization (converting any raster format to SVG) New: Added support for archive conversion (.zip, .dmg, .7z, .tar, .gz, .bz2, .xz) New: Added support for creating .dmg installers from any archives (not supported in MAS version) Fix: Fixed WebP conversion Improved: Video conversion speed increased by more than 4x