Stop uploading your files to random converter sites

Quick question: when you last converted a HEIC to JPG or merged two PDFs, where did that file go?

For most "free online converters" the answer is: their server. Your passport scan, your contract, your private photos, uploaded to who-knows-where.

Here's the thing: in 2026 this is completely unnecessary. Browsers can do almost all of it locally.

What modern browsers can do without a server

• Image conversion: Canvas API + WebAssembly decoders (HEIC, AVIF, even RAW formats)
• PDF manipulation: merge, split, rotate, compress, all in JS
• 3D file viewing: STL, STEP, OBJ, GLB via WebGL
• Dev utilities: JSON ⇄ YAML, Base64, regex, UUIDs

The file never leaves your device. You can literally turn off Wi-Fi after the page loads and it still works.

I built a collection of these

FormatMath is 50+ converters and tools, all client-side:

• HEIC to JPG (the iPhone photo problem, solved)
• Merge PDF / Compress PDF
• STEP viewer (surprisingly hard to find a free one)
• Remove photo metadata: strips GPS location before you post a photo
• Developer tools: JSON/YAML/CSV, Base64, regex tester

No sign-up, no upload, no file size limits.

The tradeoff (being honest)

Client-side processing depends on the user's device. A 200 MB PDF on an old phone will be slower than on a server. For 95% of everyday tasks, though, it's instant.

What's a tool you wish existed in the browser? I'm taking requests. 👇

Also mine: BotReady (check how AI crawlers see your site) and Fee Math (seller fee calculators).