Images
Image Compression
Image compression reduces the byte size of a picture by removing redundant or visually unimportant data, either losslessly or by discarding detail the eye barely notices.
Updated 12 Aug 2026
Two ways to make a picture smaller
Lossless compression stores the same pixels more efficiently — decode it and you get the original back bit for bit. Lossy compression permanently discards information the human eye is poor at noticing, such as subtle colour variation, which is how a photograph can shed 80% of its size with no obvious difference.
Choosing a format
| Format | Compression | Best for |
|---|---|---|
| JPEG | Lossy | Photographs, universal support |
| PNG | Lossless | Screenshots, logos, sharp edges, transparency |
| WebP | Both | Modern web delivery, 25–35% smaller than JPEG |
| AVIF | Both | Smallest files, slower to encode |
| SVG | Vector | Icons and logos — resolution independent |
Practical workflow
- 1Resize first — never ship a 4000px image into a 800px slot
- 2Pick the right format for the content type
- 3Compress at quality 75–85 for photos and compare against the original
- 4Serve modern formats with a fallback for older browsers
- 5Keep the untouched master file for future edits
Lossy compression compounds. Each save of a JPEG re-encodes and degrades it further, so always edit from the original rather than the compressed copy.
Image Compressor
Resize and compress locally with a live before-and-after preview.
Characteristics
- Lossless preserves every pixel; lossy discards perceptual detail
- Effectiveness depends on content — photos compress far better than flat graphics
- Resolution reduction is usually the largest single saving
- Metadata such as EXIF can be stripped for extra bytes
Common uses
- Speeding up web pages and improving Core Web Vitals
- Fitting attachments within email limits
- Reducing cloud storage and CDN costs
- Preparing assets for mobile apps
Advantages
- Dramatically faster page loads and better search performance
- Lower bandwidth and storage costs
- Modern formats give large savings at equal visual quality
- Browser-based tools keep private photos off third-party servers
Limitations
- Lossy loss is permanent and accumulates with re-saves
- Text and line art degrade visibly under photographic compression
- AVIF and WebP need fallbacks for legacy clients
- Over-compression produces banding and blocky artefacts
Examples
Original 4000x3000 PNG 9.8 MB
Resized 1600x1200 PNG 2.1 MB
JPEG q82 1600x1200 340 KB
WebP q80 1600x1200 240 KBFrequently asked questions
What is image compression?
Reducing an image's file size by storing pixels more efficiently or discarding detail the eye barely registers.
What is the difference between lossy and lossless?
Lossless restores the exact original pixels; lossy permanently removes information to achieve much smaller files.
Which format gives the smallest files?
AVIF, then WebP, then JPEG for photographs. Use PNG or SVG for graphics with sharp edges.
Does compressing an image reduce its resolution?
Not by itself. Resizing changes dimensions; compression changes how the pixels are stored.
What quality setting should I use?
75–85 suits most photos. Compare against the original before committing.
Related terms
PDF Compression
PDF compression reduces the file size of a PDF by re-encoding its images, removing redundant objects and compressing content streams, ideally without visible loss of quality.
OCR
OCR (Optical Character Recognition) converts text inside images and scanned documents into real, selectable and searchable characters.
Minification
Minification removes every byte a machine does not need — whitespace, line breaks, comments and long names — from code or data without changing what it does.
JSON
JSON is a lightweight text-based data format commonly used to exchange structured data between applications and APIs.
XML
XML (Extensible Markup Language) is a text format that describes data using nested, self-labelled tags, designed for documents and long-lived system-to-system messaging.
CSV
CSV (Comma-Separated Values) is a plain-text table format where each line is a row and each field is separated by a delimiter, usually a comma.
Related tools
Related guides
How to Compress Images for the Web
A practical guide to image compression: lossy vs lossless, choosing quality levels, resizing before compressing, format choice, and compressing images in your browser.
PNG vs JPG vs WebP: Which Image Format to Use
Compare PNG, JPG, WebP and AVIF on compression, transparency, quality and browser support, with a simple decision guide for photos, screenshots, logos and animation.
How to Compress a PDF Without Wrecking the Quality
Understand what actually makes a PDF large, which compression settings matter, how much size you can realistically save, and how to compress a PDF privately in your browser.
Compress PDF Without Losing Quality
Honest guide to shrinking a PDF without wrecking it: Lossless (small safe savings), Compress images (re-encode photos, keep text selectable), and Rasterize (biggest savings, flattens pages). Pick the mode that matches your file.