What to look for in the list
- Anything far wider than where it is displayed. A 4000 px photograph in a 600 px column downloads roughly five times the data it needs.
- Mixed ratios in a set that should match. Thumbnails at 4:3 and 16:9 in the same grid will never line up without cropping.
- Megapixels, not file size, when something is slow. Decoded size is four bytes per pixel and has nothing to do with how well the file compressed.
Ratios worth recognising
| Ratio | Where it comes from | | --- | --- | | 16:9 | Video, most screens, YouTube thumbnails | | 4:3 | Older cameras, many phone sensors, slides | | 3:2 | 35 mm film and most interchangeable-lens cameras | | 1:1 | Avatars, product grids, Instagram | | 1.91:1 | Open Graph and Twitter cards |
Nothing is uploaded
Each file is decoded by your browser to read its header. That is the whole operation — no upload, no server, and it works offline.
Questions
Why show the ratio as 16:9 rather than 1.78?+
Because that is how ratios are specified — in a design brief, a platform's requirements, a CSS aspect-ratio rule. The fraction is reduced to whole numbers where it can be; past 40:40 the simplified form stops being readable and a decimal is shown instead.
Can I check a whole folder?+
Up to the batch limit on the drop area — one file anonymously, forty with a free account. Dropping a folder's worth at once is the point: spotting the one image that is 6000 px wide is much easier in a list than one file at a time.
Does it read EXIF orientation?+
The dimensions are what the browser decodes, which already accounts for the orientation flag. That is what a browser will render, so it is the number that matters for layout.
Why does megapixels matter?+
It predicts memory and processing cost better than either dimension alone. A browser holds a decoded image as four bytes per pixel, so a 24 MP photograph occupies about 96 MB of RAM regardless of how small the JPEG was.