Image compressors compared — an honest look

I built Tinier because I thought the existing online image compressors got something important wrong: most of them quietly trade lossless for quantization, hide behind a privacy policy instead of structure, or paywall the file sizes that matter. But claiming to be different is cheap. This page lays out the criteria honestly, includes Tinier among the others, and tells you where Tinier loses too. If you came here looking for a definitive answer, the answer is: it depends on what you need. Read on.

The criteria that actually matter

Most "best image compressor" articles compare on whether the website looks nice or how many formats it claims to support. Those are not the criteria that change the outcome of your work. The ones that do are below.

Where the compression actually happens

Server-side compressors upload your image, process it remotely, and send the result back. Browser-only compressors run the work locally in your browser via WebAssembly. The server-side approach takes a round-trip through the network and puts your file briefly on someone else's hardware. The browser-only approach is private by construction and faster on photos under 10 MB. Server-side has the upper hand on very large files and exotic formats; browser-only has the upper hand on everything else.

Whether "lossless" actually means lossless

For PNG, the most-touted compression number — often 60–70% — is achieved by quantizing the image, that is, reducing the palette from 16 million colors to 256 or fewer. Quantization can produce a result that looks identical at a glance but is not pixel-identical to the input. Calling that "lossless" is a stretch, and several popular tools do it. True lossless PNG optimization (OxiPNG, pngcrush) typically saves 10–20% — modest, but actually lossless. If you need 60% PNG savings and an exact pixel match, you cannot have both, and any tool claiming otherwise is bending the definition.

File size limits and paywalls

The most popular tools cap free uploads at 5 MB or 10 MB and ask you to subscribe for larger files. The cap is a marketing decision, not a technical one — the same tool, paid, can handle 50 MB. Browser-only tools cap based on browser memory, which is usually 50 MB to a few hundred MB depending on your device. There is no paywall; the limit is real.

Whether you keep control of the quality dial

Some tools expose a quality slider, some hide it behind an "auto" mode that picks for you, and some give you only "Lossless" vs "Lossy" as binary choices. Auto modes work most of the time but make a few percent of images look noticeably worse than they should. A real, exposed slider lets you see the trade-off and pick where you want to land.

Where each approach wins

Server-side compressors

Win on: aggressive PNG quantization (when you accept the trade-off), exotic format conversion, very large files past browser memory, batch processing through an API. The mature ones have well-tuned encoders and good user experience.

Lose on: privacy (your file is on their server), speed for files under 10 MB (the round-trip dominates), file size paywalls on free tiers, and sometimes on labeling — quantization sold as lossless is the most common honesty gap.

Browser-only compressors

Win on: privacy by construction (files never leave your device — you can disconnect your internet and the tool keeps working), speed on small-to-medium files, and honest labeling because there is no "free vs paid" tier to obscure. No login, no rate limits, no paywall on file size up to browser memory.

Lose on: very heavy compression that needs more compute than a browser can spare (quantized PNG output is the main one — real lossless PNG savings are 10–20%, not 50%). Maximum file size is bounded by browser memory, typically 50 MB. The tool stops working past that.

Where Tinier fits — and where it does not

Tinier is browser-only. It uses MozJPEG for JPG, OxiPNG for PNG, and libwebp for WebP — all open source, all running as WebAssembly on your device. The quality slider is real and exposed. The file size cap is 50 MB, which is browser memory, not a marketing decision. There is no signup, no rate limit, no upload to any server.

Where Tinier wins today: JPG photos compress 60–80% smaller in 2–4 seconds, with a real quality slider you control. PNG compresses losslessly without any quantization disguised as lossless. WebP compresses with libwebp, the same encoder Chrome uses internally. Privacy is structural — you can verify it by disconnecting your internet after the page loads and watching the tool keep working.

Where Tinier does not win: if you need 50% savings on a flat PNG illustration, you need quantization and Tinier does not offer it yet. Server-side tools that quantize will give you a smaller file today. I will offer quantization later as an opt-in, explicitly-labeled mode — never disguised as lossless. Tinier also does not yet support AVIF, HEIC, lossless WebP, format conversion, or batch sizes beyond 10 files. If your workflow needs any of those, a server-side tool may be the better fit right now.

A simple decision tree

Try Tinier on your own image

The dropzone above the fold is the entire app. Drop your file and see the result locally — nothing leaves your device. If the savings number disappoints, that is honest information about the file you have. If it does what you need, that is a comparison that matters more than any table.