Working notes on the decisions behind everyday media tasks: which format to pick and why, what a quality slider is really adjusting, how image dimensions map onto PDF pages, and which images are worth tracing to vectors. Written from practice rather than from specifications, and revised as the answers change.
8 guides. Written and maintained in English.
Video size is governed by four settings that interact. Change them in the right order and you can often cut a file by three quarters with no visible difference.
Read the guideBitrate, sample rate and bit depth get confused constantly. Here is what each one controls, and the settings that make sense for speech, music and archiving.
Read the guideTracing converts pixels into shapes, which works brilliantly on logos and badly on photographs. Understanding why tells you which images are worth attempting and how to set the parameters.
Read the guideImages are usually the largest thing on a page and the most common cause of a poor Largest Contentful Paint score. This is the sequence of fixes that actually moves the number.
Read the guideThere are two fundamentally different ways to combine PDFs, and they produce very different files. One preserves everything, the other deliberately destroys things. Both are correct in the right situation.
Read the guideQuality 80 is not 80 percent of anything. Here is what the number actually controls, why it behaves differently on different images, and a repeatable way to find the lowest setting you can get away with.
Read the guideFour formats cover almost every job on the web, and picking the wrong one costs you either file size or quality. This guide explains what each format actually does and when to reach for it.
Read the guideImages have pixels, PDF pages have physical dimensions, and the conversion between them is where most problems start. This explains the relationship and how to control it.
Read the guide