Free online image tools in a grid: rows are what you have, columns are what you need. Each square says what changes on the way: transparency, animation, quality and size. Click one for the details and the right tool.
Each destination has its own size, format and file-size limits. Choose one to get the spec and the tools, in the order you'd use them.
Tools that change the pixels, the dimensions or the file size, and leave the format alone.
Pick a test image or use your own. Your browser encodes it as JPEG, WebP, AVIF and PNG at the quality you set. It then decodes each result and measures how far it drifted from the original. That measure is PSNR: higher means closer, and above about 40 dB most people can't see a difference. Click the image to choose which part to zoom into.
Tiles are 3× enlarged. Each browser ships its own encoders, so the same settings give different bytes in Chrome, Safari and Firefox. When a browser can't encode a format it returns a PNG instead, which this page detects.
Tick what your image needs. Formats that can't do it fade out, and what's left is your shortlist.
A JPEG is a chain of marker segments. Camera details, the time and often the exact GPS position sit in an APP1 segment as a small TIFF file, separate from the pixels. This reader walks through the segments of a real JPEG and decodes the EXIF tags. It then strips them two ways and checks what changed. The sample is a photo your browser just encoded, with EXIF data written in.
Identify a file by its first bytes, not its extension. Magic bytes are in hex, and .. marks bytes that vary from file to file.
The other toolboxes, with a typical job for each.