Why compress JPEG photos?
A single photo from a smartphone or DSLR can be 3–10 MB straight from the camera. That is far more than web pages, email attachments, or social media uploads need. JPEG compression re-encodes the photo at a lower quality setting, discarding detail your eye barely registers, to produce a file that is 70–90% smaller and virtually indistinguishable at normal screen sizes.
For websites, heavy images are the leading cause of slow page loads and poor Core Web Vitals scores. A product photo compressed from 4 MB to 300 KB loads in a fraction of a second and keeps visitors from bouncing. For email, most servers cap attachments at 10–25 MB; compressing a batch of holiday photos to 200–400 KB each lets them go through instantly. For social media, platforms like Instagram and Twitter re-compress every upload — sending a pre-compressed photo prevents a second lossy pass and gives you control over the final quality.
How to compress a JPEG file
- Drop your files — drag JPG or JPEG images onto the upload zone, click to browse, or paste from clipboard. Up to 30 at once.
- Set the quality — 80% is the default and a safe starting point. Lower for a smaller file, higher to protect fine detail.
- Click Compress — the tool re-encodes each photo in your browser using the Canvas API. Your files stay on your device.
- Check the savings and download — each file shows its before and after size plus the percent saved. Download individually or grab them all as a ZIP.
How JPEG compression works
JPEG uses a technique called Discrete Cosine Transform (DCT) to represent image data as frequency components rather than raw pixels. High-frequency detail — fine textures, sharp edges, subtle gradients — is stored with less precision at lower quality settings, which is where the size reduction comes from. At 80% quality, most of the discarded detail is in areas where the human visual system is least sensitive: high- contrast edges and uniform regions both tolerate compression well, while faces and fine text degrade more visibly at low settings.
Because each re-encoding pass introduces new rounding errors, it is important to always compress from your original file, not from a previously compressed copy. Keep a high-quality master and compress once per destination.
Choosing the right quality setting
| Quality | Best for | Typical file size |
|---|---|---|
| 90–100% | Archival, print, images with text or logos | Large — minimal savings |
| 75–85% | Web photos, email, social media — the sweet spot | 70–90% smaller, loss hard to spot |
| 60–70% | Thumbnails, previews, tight size limits | Very small — artifacts on edges and text |
After compressing, zoom into text, faces, and hard edges to check for artifacts. Those areas degrade most visibly. Images that are mostly sky, water, or smooth backgrounds tolerate lower settings well.
Compressing JPEG for the web
Web performance guidelines recommend keeping images under 200 KB for most page elements. 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 that looks sharp at its display size — a photo displayed at 800 px wide does not benefit from being 4000 px wide.
For even smaller files after compressing, consider converting to WEBP. WEBP typically delivers 25–35% smaller files than JPEG at the same visual quality, and all modern browsers support it.
Compressing JPEG for email
Most email providers (Gmail, Outlook, iCloud) impose attachment limits of 10–25 MB. A batch of ten uncompressed photos from a recent trip can easily exceed that limit. Compressing each photo to 200–500 KB brings ten photos to under 5 MB total — well within any provider's limit and faster to download on the recipient's end.
If the photos are going to print, keep the quality at 90% or higher to preserve enough detail for standard print resolutions (around 300 PPI). For digital sharing only, 80% is plenty.
Compressing JPEG for social media
Instagram, Twitter, Facebook, and LinkedIn all re-compress every photo you upload. Sending a large, high-quality original means the platform applies its own compression algorithm on top of yours — sometimes aggressively. Pre-compressing your photo at 80–85% quality before uploading gives you control over what the platform starts with, often producing a better-looking final result than uploading raw and letting the platform decide.
Pair this with resizing to the platform's recommended dimensions — use the Image Resizer before compressing to get both the pixel size and file size right in one workflow.
Compressing JPEG vs resizing
Compressing keeps the same pixel dimensions and lowers encoding quality to cut file size. Resizing changes the actual pixel count. For the smallest possible result, do both: use the Image Resizer to trim dimensions first, then compress here. A 4000×3000 photo resized to 1280×960 and compressed at 80% can drop from 5 MB to under 150 KB.
Need to compress PNG or WEBP too?
This tool is focused on JPEG. If you need to compress PNG or WEBP images alongside JPEGs in the same batch, the Image Compressor handles all three formats at once, including palette-based PNG compression.
Privacy
Every byte stays in your browser. No upload, no temporary server file, no log. Photos are re-encoded in a <canvas> element using the browser's built-in JPEG encoder. Your files never leave your device.