Most free "compress this image" or "convert this PDF" sites work the same way: upload your file to their server, process it, send it back. I built ToolHub to avoid that where possible — most of the 45+ tools on there run entirely in the browser, so the file never actually leaves your device.
A quick sample of what's on there:
Image tools — compressor, resizer, cropper, format conversion, all processed client-side with a live before/after preview
PDF tools — merge, split, compress, and conversion to/from Word, Excel, and PowerPoint (that last one was the hardest to build — no good client-side library exists for generating real .pptx files, so I ended up hand-building the OOXML structure and verifying it with python-pptx before shipping)
Developer tools — JSON formatter, regex tester, hash generator, Base64, UUID generator
Color tools — color picker (samples real pixel values from an uploaded image), palette generator, format converters
A couple of social tools — YouTube thumbnail downloader, Instagram image resizer
Stack: React + Vite frontend, Node/Express/MongoDB backend for the account/history/favorites side — the file processing itself never touches the server.
Still early on distribution. If anyone's got thoughts on the tools, or on "browser-based, no upload" as a real differentiator vs. just another free tool site, I'd like to hear it.
Top comments (1)
Hand-building OOXML for the pptx export is the part that stands out, that format is genuinely painful to generate correctly since PowerPoint is picky about relationship IDs and content types even when the XML looks valid. Verifying against python-pptx as a sanity check is smart. On the "no upload" differentiator question, I'd lean into it hard for anything work related, PDFs with client contracts or financial data going through a browser tab instead of a random server is a real selling point, not just a privacy nice-to-have.