Why compress images?
Large images are the number-one cause of slow web pages, blown email attachment limits, and wasted storage. A single phone photo straight from the camera can be 4–8 MB — far more than any web page, email, or social post needs. Compressing trims that down by re-encoding the image at a lower quality setting, discarding detail your eye barely registers. The result loads faster, attaches without complaint, and looks practically identical at normal viewing sizes.
For websites, Google's Core Web Vitals directly penalise heavy images. A compressed photo that loads in 200 ms instead of 2 seconds keeps visitors on the page and helps search rankings. For email, most servers reject attachments over 10–25 MB; a batch of holiday photos compressed to 200–400 KB each goes through instantly. For cloud storage, compressing before uploading means your free tier lasts longer.
How to compress an image
- Drop your files — drag JPG, PNG, or WEBP images onto the upload zone, click to browse, or paste from clipboard. Up to 30 at once.
- Set the quality — 80% is a safe default. Lower for smaller files, higher to protect fine detail.
- Click Compress — decoding and re-encoding happen locally with the Canvas API. Your files stay on your device.
- Check the savings and download — each file shows its before/after size and percent saved. Download individually or grab them all as a ZIP.
How much smaller will my image get?
Results vary by content and starting quality, but here are realistic expectations:
- Phone photo (4–8 MB JPG) at 80% quality typically compresses to 400–800 KB — an 80–90% reduction with no visible loss at screen size.
- Screenshot or graphic (1–2 MB PNG) with palette quantization at quality 70 usually lands around 100–300 KB, depending on how many distinct colors the image uses.
- Already-compressed JPEG (shot at 95% or exported from a photo editor) compresses well at 75–80%. An already-compressed file at the same setting gains less — if your image barely shrinks, it was already well-optimised.
For the absolute smallest file, resize the image to its display dimensions first using the Image Resizer, then compress here. A 4000×3000 photo resized to 1280×960 and compressed to 80% can drop from 5 MB to under 150 KB.
Lossy vs lossless compression
JPG and WEBP use lossy compression: each encoding cycle permanently discards some pixel data. This is why quality drops if you repeatedly open, edit, and re-save a JPG — each save is a new compression pass. To avoid this, always compress from your original file, not from a previously compressed copy. Keep the high-quality master and compress once for each destination.
PNG uses lossless compression by default, which means re-saving it never degrades quality — but also means the format itself has no quality slider. This tool compresses PNGs through palette quantization (reducing the number of colors), which does introduce some data loss in exchange for significantly smaller files.
Compressing vs. resizing
These solve different problems. Compressing keeps the same pixel dimensions but lowers encoding quality to cut file size. Resizing changes the actual pixel count — a 4000×3000 photo down to 1280×960. For the smallest possible result, do both: use the Image Resizer to trim dimensions first, then compress here.
Choosing a quality setting
| Quality | Best for | Trade-off |
|---|---|---|
| 90–100% | Archival, print, images with text or logos | Largest files, minimal savings |
| 75–85% | Most web photos — the sweet spot | Big size drop, loss hard to spot |
| 50–70% | Thumbnails, previews, tight size limits | Visible artifacts on detail and edges |
After compressing, zoom into text, hard edges, and faces to check for artifacts — those areas degrade most visibly. If you spot blocky patches around text at 80%, try 85%. Images that are mostly sky, water, or smooth backgrounds tolerate lower settings well.
Compressing PNG images
PNG is a lossless format, so re-encoding it at a lower quality does nothing — there is no quality dial in the format itself. Instead, this tool compresses PNGs the way apps like TinyPNG do: by quantizing the image to a smaller color palette. The quality slider maps to the number of colors kept (from 256 down to a handful), so a lower setting yields a smaller file with more visible posterization. Transparency is preserved throughout. This works best for graphics, logos, and screenshots with flat color regions. For photographic PNGs with smooth gradients, converting to WEBP usually produces an even smaller file, and PNG to JPG shrinks them further still if you do not need transparency.
Compressing images for the web
Web performance guidelines recommend keeping page images under 200 KB each. Hero images and full-width banners can go up to 400 KB if they are the centrepiece of the design, but thumbnails, card images, and sidebar graphics should be well under 100 KB. Aim for the smallest file size that looks sharp at its display size — an image displayed at 800 px wide does not benefit from being 4000 px wide.
If you need even smaller files after compressing, consider converting JPG and PNG images to WEBP. WEBP typically delivers 25–35% smaller files than JPG at the same visual quality, and all modern browsers support it.
Privacy
Every byte stays in your browser. No upload, no temporary server file, no log. JPG and WEBP are re-encoded in a <canvas> element using the browser's built-in encoders; PNG quantization runs locally in JavaScript. Your files never leave your device.