Image guides
Practical, in-depth writing on image formats, compression, page speed and the dimension standards that trip people up, written to be useful whether or not you ever use one of our tools.
Which image format should you actually use?
Six formats and one decision: what each is good at, where each falls apart, and how to choose without having to think about it again.
Read the guide Performance · 11 min readHow to compress images for a faster website
Images are usually the heaviest thing on a page and the easiest to fix. This is the workflow in the order that saves the most bytes, with real numbers from a worked example.
Read the guide Reference · 10 min readPassport photo sizes: a reference guide
Photo requirements are specified in millimetres, judged by a human, and change without notice. This is what the numbers mean, how they convert to pixels, and why photos get rejected.
Read the guide Reference · 8 min readSocial media image sizes
Every platform crops uploads to its own ratio. Pre-sizing means you decide what stays in frame instead of an algorithm deciding for you.
Read the guideWhy we write these
Most questions we get are about a decision more than a tool. Which format should this be? How small does it need to be? Why did the passport office reject it? A button cannot answer that, so we write it down properly instead.
Everything here is checked against how browsers and encoders actually behave, and we say when something is a rule of thumb rather than a fact. Where a figure can change (platform dimensions, government photo rules) we say that too, and point you at the authority that sets it.
Found something wrong or out of date? Tell us and we will correct it.