Compress PNG images losslessly — in your browser

Drop a PNG and Tinier optimizes it locally on your device with OxiPNG, a Rust-based PNG optimizer that re-encodes pixel data without changing a single pixel. Typical savings are 10–20% on real-world PNGs — modest, but actually lossless. Nothing uploads. Up to 50 MB per file, 1 to 10 files at a time.

What "lossless" really means for PNG

A lossless PNG optimizer must produce a file that decodes to the exact same pixels as the input. Every red value, every green value, every blue value, every alpha value — bit-identical. OxiPNG does this by trying different filter strategies, removing redundant chunks like timestamps and editor metadata, and recompressing the IDAT stream more efficiently. The image you see does not change.

Some online PNG compressors claim "lossless" while quietly running a quantization pass — reducing the palette from 16 million colors to 256, for example. That can save 40–50% on flat illustrations and looks identical at a glance, but it changes the image. If you compare the two files pixel by pixel, they differ. Tinier will not call that lossless. When quantization ships, it will be a separate, opt-in mode with its own slider.

When PNG cannot be made smaller

If your PNG was already exported by Photoshop, Figma, or another modern tool with optimization enabled, OxiPNG may only shave 1–3% off — sometimes less. Tinier tells you when this happens instead of pretending. The status reads "already well optimized" and you can either accept the marginal save or download the original. No tool can losslessly compress a file below its information-theoretic limit, and Tinier will not pretend otherwise.

The slider controls effort, not quality

Because PNG compression in Tinier is lossless, there is no quality dial. The slider you see controls how hard OxiPNG tries to find a smaller encoding. The default of 50 maps to OxiPNG level 3 — fast, roughly 85% of the maximum savings. Pushing to 100 maps to level 6, which can take 10 times longer on a 10 MB PNG and typically gains only 1–3 extra percentage points. Stay at the default unless you really need every byte.

Why compress PNG in the browser instead of on a server?

Server-side PNG compressors upload your image, run OxiPNG (or equivalent) on a backend, and send the result back. The OxiPNG step is identical; the round-trip is the difference. Tinier skips the round-trip and runs OxiPNG locally via WebAssembly, which means your PNG is never on someone else's hardware, even briefly. For a logo or screenshot you are sharing on the web, that is structural privacy — not a checkbox in a privacy policy.

Frequently asked questions about PNG compression

Is PNG compression really lossless?

In Tinier, yes. Tinier uses OxiPNG, which strips redundant metadata and re-encodes pixel data without changing a single pixel. The output looks pixel-identical to the input under any inspection. Some other tools advertise "lossless" PNG compression but quietly quantize the image to a smaller color palette — that is not lossless, that is a different image.

Why does my PNG only compress 10–20%?

That is the honest ceiling for lossless PNG optimization. PNG is already a compressed format — the gains come from finding a more efficient way to represent the same exact pixels, not from throwing data away. If you need 40–50% savings on a PNG, the only path is quantization (reducing the palette), which changes the image. Tinier will offer quantization later as an explicit, opt-in mode, not disguised as lossless.

What does the slider control on PNG?

Optimization effort, not quality. OxiPNG tries harder to find a smaller encoding when the slider is higher. Effort 50 (the default) maps to OxiPNG level 3 — about 85% of the savings of the maximum effort, in a fraction of the time. Going to 100 typically buys 1–3 extra percentage points and can take 10x longer on large files.

Can Tinier compress PNG with transparency?

Yes. Tinier preserves the alpha channel exactly. Transparent PNGs (logos, UI assets, screenshots with transparency) compress the same way as solid PNGs and the transparency is bit-identical in the output.

Other formats Tinier compresses