Image Compression Guides
Start with the job you need to finish: get a photo under an upload limit, choose JPG or WebP, or check why a smaller image looks blurry. These guides explain the settings and their limits, with links back to the tool when you're ready to try them.
Practical size guides
Convert JPG to WebP
Compare formats, choose file size or quality, and download WebP images without uploading your photos.
Compress JPG to 20KB, 50KB, 100KB or 200KB
The bits-per-pixel rule that predicts quality, the right dimensions for each limit, and one-click presets.
Passport and ID Photos
Check official dimensions first, then reduce the JPG to the portal's actual file-size limit.
Email and WhatsApp Photos
Make a batch easier to share without compressing every image more than its purpose requires.
Learn about image compression
From JPG to WebP: The Quiet Mathematics of Guessing Well
Block prediction, an integer cousin of the DCT, the plus-and-minus Walsh–Hadamard transform and arithmetic coding, with worked examples.
The Beautiful Mathematics Behind Every JPEG
How a 200-year-old idea about heat became the cosine transform in every photo, with a live worked example and the history of compression.
JPEG vs PNG vs WebP: Which Format Should You Use?
A comprehensive comparison of the three most popular image formats — when to use each, quality differences, and browser support.
How JPEG Compression Works — A Visual Guide
Dive into DCT transforms, quantization matrices, and Huffman coding. Understand why JPEG artifacts appear and how quality settings affect file size.
Reduce Image Size While Keeping Useful Detail
A practical workflow for size limits, quality settings, resizing, and honest before-and-after checks.
Best Image Sizes for Social Media in 2026
Complete reference guide for Facebook, Instagram, Twitter/X, LinkedIn, Pinterest, TikTok, and YouTube — dimensions, aspect ratios, and file size limits.
Lossy vs Lossless Compression: What's the Difference?
Understand the two fundamental approaches to data compression, how they apply to images, and when each type is the right choice.
Ready to put this knowledge into practice?
Compress your JPEG images for free — no uploads, 100% private, right in your browser.
Open CompJPG Compressor