A Practical Guide to Image Compressor

Photos straight from a phone or camera are usually much larger than they need to be for a website, an email attachment, or a content upload limit. The Image Compressor shrinks JPG, PNG, and WebP files by re-encoding them entirely in your browser, so nothing you upload here actually leaves your device.

How the compression actually works

When you drop an image into the tool, it's drawn onto an HTML canvas element and re-encoded from that canvas — the same basic technique browsers use internally to resave images. That has two practical effects worth knowing about:

• Metadata is dropped. Re-encoding through canvas doesn't carry over EXIF data such as camera settings or embedded GPS coordinates, so a compressed image is also a bit more private by default.
• You'll never get a larger file than you started with. If none of the compression attempts beat the original file size, the tool keeps your original file instead of handing back something bigger.

JPG and WebP use quality-based lossy compression — the slider controls how aggressively fine detail is discarded. PNG works differently: since PNG is normally lossless, the "quality" slider instead controls how many colors are kept in the image's color palette. That's why moving the slider on a PNG that already uses very few colors, like a flat-color logo, often does very little, while a PNG screenshot full of gradients and photos will shrink noticeably at lower settings.

Step-by-step: compressing your images

1. Upload. Drag and drop, or click to browse, one or more JPG, PNG, or WebP files.
2. Pick a quality level. The slider defaults to 70%, a balance most people never need to change. Lower it for smaller files if some visible quality loss is acceptable; raise it if the image needs to stay crisp.
3. Optionally change the output format. Leave it on "Original" to keep the same file type, or convert to WebP for typically smaller files, JPG for maximum compatibility, or PNG if you need transparency preserved.
4. Compress and compare. The before/after preview and the percentage saved update per image, so you can judge the trade-off before downloading.
5. Download. Save files individually or grab the whole batch at once.

Choosing a quality level and format

For most web use, 60–75% quality on JPG or WebP is a reasonable starting point — go lower for large hero images a visitor will scroll past quickly, and keep it higher where fine detail matters, like product photography or screenshots containing text. WebP generally produces smaller files than JPG at a similar visual quality, so it's worth trying "Convert to WebP" even for photos you weren't planning to otherwise edit. PNG is best reserved for images that need transparency or that are mostly flat color and text — logos, icons, diagrams — since compressing a real photograph as PNG usually produces a bigger file than JPG or WebP at an equivalent visual quality.

Troubleshooting

• "My PNG barely got smaller." Expected for PNGs with few distinct colors — there isn't much palette size left to trim. Try converting to WebP or JPG instead if you don't need transparency.
• "The compressed image looks blocky or has visible artifacts." The quality slider was set too low for that particular image. Recompress from the original at a higher setting — the tool always encodes fresh from your original file, never from an already-compressed copy, so nothing is permanently lost until you overwrite the source.
• "Nothing changed after I clicked compress." If the format is set to "Original" and the image was already efficiently encoded, the compressor may not find a smaller result and returns your original file unchanged rather than a larger one.
• "It's slow with a lot of images." Because everything runs on your device's own CPU instead of a server, compressing dozens of large images at once uses noticeably more memory and time than a handful of small ones — working in smaller batches helps on lower-powered devices.

Compress or resize?

Compression changes file size without changing pixel dimensions. If an image is also physically larger than it needs to be — say, a 4000px-wide photo displayed at 800px on a page — resizing it first with the Image Resizer will usually save far more space than compression alone, since you're reducing the actual pixel count rather than just how efficiently those pixels are encoded. For the smallest possible file, resize to the dimensions you actually need, then compress the result.

Ready to try it? Open the free Image Compressor and drop in your first image — no account, no watermark, and nothing leaves your browser.