Images & VideoUpdated 17 October 2026
Images, video and audio
Choosing between JPEG, PNG, WebP and AVIF, resizing versus compressing, why MP4 is not a codec, and shrinking a video or GIF without ruining it.
Image questions look like format questions and are usually resolution questions in disguise. A photograph four thousand pixels wide shown in an eight-hundred-pixel column carries far more data than anyone will see, and no compression setting fixes that as cheaply as resizing does. Video has the same shape of problem with more moving parts. MP4 is a container, not a codec, so two files with the same extension can behave completely differently, and when a clip has to be smaller the order in which you cut bit rate, resolution and frame rate decides whether it still looks right. The guides here cover images, GIFs, video, extracted audio and subtitles, and each one ends at a tool on this site that does the job in your browser.
20 guides5 subjects
20 guides
Opening a PSD or AI file when you do not have Adobe software
Designers send working files because that is what they have open. You only need the picture. Both Photoshop and Illustrator files usually carry a ready-made copy of it.
Camera RAW files, and the JPG hidden inside every one
A RAW file is not a photo. It is the sensor's measurements, waiting to be developed. But every camera also tucks a finished JPG inside, and that is often all you need.
iPhone photos in HEIC: opening, sharing and converting them
You send a photo from your iPhone and the other person gets a file they cannot open. The photo is fine. The format is the problem, and it has three fixes.
Making a GIF that is not 40 megabytes
A five-second clip becomes a 40 MB GIF and a 900 KB MP4 of identical quality. GIF is not a video format, and that is the whole explanation.
Reading text off an image: what OCR gets right and where it fails
The difference between 99% and 80% accuracy is usually the photo, not the engine. Most of the fix happens before any text is recognised.
MP4 is not a codec: containers, codecs and why a file will not play
Renaming a file to .mp4 changes nothing about what is inside it. The extension names the box; the thing that fails to play is the contents.
Compressing a video without ruining it
A 200 MB clip has to reach 25 MB. There are three dials that make it smaller and only one of them is usually the right one to turn first.
Getting the audio out of a video, and what quality survives
The audio in a video is already a separate stream. Pulling it out can be a copy rather than a conversion, and the difference is audible.
Subtitles: SRT files, embedded tracks and burned-in captions
Captions can be a separate file, a track inside the video, or pixels drawn permanently onto the frames. Only one of those is reversible.
Favicons: the sizes that still matter and the ones that do not
The advice online still lists a dozen icon sizes from 2014. Four files cover essentially everything today, and one of them is not an icon at all.
Watermarks and annotations: drawing on top of an image
Marking a proof and pointing at a bug in a screenshot are the same operation with very different stakes.
Rotate, flip and sharpen: the small fixes, and which ones cost quality
Your phone photo appears sideways on the web but upright in the gallery. Nothing is broken, and the fix is one byte.
Base64 images: when inlining helps and when it costs you
A data URI embeds the picture in the markup. That is occasionally the right call and usually a way to make a page slower.
Cropping well: aspect ratios, the rule nobody needs, and safe areas
Every platform re-crops your image to its own ratio. If you do not decide where the subject sits, an algorithm will decide for you.
Screenshots that actually help: annotation, redaction and what leaks
A black box over text in a screenshot really does delete it, unlike in a PDF. Blurring, on the other hand, has been reversed.
JPEG, PNG, WebP or AVIF: picking the right image format
Saving a screenshot as JPEG makes the text fuzzy. Saving a photo as PNG makes the file eight times larger. Both mistakes come from the same gap in knowledge.
How image compression works: lossy, lossless, and the quality slider
The number in the quality box is not a percentage of anything. Knowing what it really controls explains most of the odd results people get.
Resize or compress? The difference that decides your file size
A 300 DPI setting does nothing for an image on a website. Pixels are the only unit the screen understands, and understanding that fixes a lot of frustration.
How AI background removal works, and where it still fails
The model is not "finding the person". It is assigning every pixel a probability of being foreground, which explains exactly why hair and glass give it trouble.
Image optimisation for web performance: the four things that matter
Most pages ship images several times larger than they display, in a format from 1992, with no dimensions set. Fixing those three things is most of the work.