Image Compressor
Shrink an image's file size with a quality slider.
Overview
The Image Compressor shrinks the file size of a photograph by re-encoding it at a lower quality setting, with a slider that trades visual fidelity for kilobytes. Upload a JPEG, PNG or WebP, pick a quality, and the tool returns a smaller copy alongside a before/after byte count.
Site owners use this to reduce image file size for faster page loads, hit a CMS upload limit, fit an attachment under an email size cap, or trim payloads before bundling assets into a mobile app. It is the practical alternative to opening every file in Photoshop and re-exporting one by one.
How it works
For JPEG the encoder runs a discrete cosine transform on 8x8 blocks, quantises the resulting coefficients using a table scaled by the quality slider, and then entropy-codes the residuals with Huffman or arithmetic coding. Lower quality means coarser quantisation and shorter codes, which produces visible blocking artefacts only at very low settings.
For PNG the savings come from a different mechanism — PNG is lossless, so the tool re-runs the deflate compression pass and prunes ancillary chunks like comments and ICC profiles. WebP supports both lossy (predictor + DCT-style transforms) and lossless modes, and the encoder picks the right pipeline based on the quality slider.
Examples
Before: photo.jpg (4.8 MB, quality 95)
After: photo.jpg (1.1 MB, quality 80) — 77% smaller
Before: screenshot.png (2.1 MB, full sRGB profile)
After: screenshot.png (340 KB) — same pixels, smaller deflate
Before: hero.jpg (3.2 MB)
After: hero.webp (640 KB) — convert + compress combined
FAQ
What quality should I pick?
JPEG quality 80-85 is the usual sweet spot for photographs — visually indistinguishable from 95 but typically half the file size. Drop to 70 for thumbnails.
Does compressing twice make the file smaller still?
No — JPEG quantisation is lossy, and repeated re-encoding only adds more artefacts without further size gains. Always compress from a high-quality source.
Will PNG quality affect the look?
Standard PNG compression is lossless, so the pixels are byte-identical. The "quality" slider for PNG controls deflate effort and palette quantisation if you opt into a colour-reduced variant.
Can I compress while keeping transparency?
Yes for PNG and WebP. JPEG has no alpha channel; the tool flattens against white if you target JPEG output.
Is the original ever modified?
No — the input bytes are read, processed in memory, and the compressed copy is returned as a fresh download. Your local file is untouched.