ToolKoala
Honest comparisons and engineering notes on browser-based, privacy-first tools.
Turning a stack of photos or scans into a single PDF is a two-minute job — if the tool doesn't upload your files. Here's how to do it in your browser, and how to keep the pages sharp and in order.
Try Image to PDF→Most "free online" converters and compressors upload your file to a server. Here's what that means for your privacy, how to tell which tools do it, and how a browser-only tool avoids it entirely.
Try Compress Image→2048 looks complicated but the core is one small function reused four times. Here's the whole game loop — sliding, merging, spawning, and detecting game over — the way I built it for ToolKoala.
Try 2048→A plain-English guide to the four image formats that matter — what each is good at, where each falls apart, and a simple rule for picking one. With a free converter to switch between them.
Try Convert Format→Every photo you take carries hidden metadata — often including the exact GPS location, your camera, and the timestamp. Here's what EXIF is, why it matters before you post, and how to strip it in your browser.
Try EXIF Remover→You can drop a logo into the center of a QR code and it still works — thanks to built-in error correction. Here's how that works, how big the logo can be, and how to make one in your browser.
Try QR Generator→Grabbing the exact colors from a photo, screenshot, or logo is the fastest way to build a palette that actually matches. Here's how to pick colors from an image and turn them into HEX, RGB, and HSL — in your browser.
Try Color Picker→X-Sudoku adds just one rule to classic Sudoku — both main diagonals must also hold 1–9. Here's how that changes the solve, with a free board to try.
Try Diagonal Sudoku (X-Sudoku)→
Engineering
ToolKoala ships over 100 file-processing tools in a single React + Vite app. The main bundle started at 6 MB. We got it to 307 KB — a 95% reduction — by fixing six specific things. Here's exactly what they were, in order of impact.
OCR
I tested 4 OCR tools on 100 real-world images — receipts, screenshots, handwriting, multi-language docs, low-light photos. Here are the actual character accuracy numbers, not the marketing claims.
Try Image to Text (OCR)→
Images
I tested 6 tools on 30 images — product photos, portraits, hair, fur, glass. Here's which one actually wins, where each fails, and why the answer depends on what you're shooting.
Try Remove Background→
Video
Most "online video compressors" send your file to a server. Here's how we built one that runs 100% in your browser using FFmpeg.wasm — and how you can verify it yourself in 10 seconds.
Try Video Compressor→