For a photograph, start with a sensible JPEG
JPEG is a familiar choice for still photographs and is widely accepted by websites and applications. It uses lossy compression, so a smaller file can cost some detail. Compare faces, fine texture and high-contrast edges when judging the result.
Export from the original and inspect the size people will actually see. A small listing image may not need full camera resolution. Keep an untouched original for later use. Repeatedly editing an already compressed copy leaves fewer options when another destination needs more detail or a different crop.
For small text and clean edges, compare PNG
PNG uses lossless compression and supports transparency. It is often a useful starting point for interface screenshots, diagrams and graphics with crisp text. Those properties do not guarantee the smallest file, especially when the subject is a detailed photograph.
Try a crop containing the screenshot’s smallest labels. If a JPEG export puts visible fuzz around letters, compare PNG or a suitable lossless export. Preserve the information the reader needs. A small file saving is not useful if a model number, chart label or important instruction becomes difficult to read.
For web delivery, test WebP as well
WebP supports lossy and lossless compression and can include transparency. Google’s documentation describes a format designed for efficient web images. It can be useful when the destination accepts it, but file size still depends on the picture and the export settings.
Displaying an image and exporting it are different capabilities. A browser may decode a format while a particular conversion path exports something else. If a tool reports a PNG result after a requested WebP export, check the actual output. Renaming a .png file to .webp does not convert its contents.
Treat transparency as a requirement
A transparent logo needs a format that preserves its background. JPEG has no alpha channel. When converting a transparent image to JPEG, choose a deliberate background colour and inspect the result against the surface where it will appear.
A logo that looks clean on a white preview can have a visible rectangle on a dark page. Try the graphic on light and dark backgrounds when both matter. If transparency is essential, use a suitable PNG or WebP output and check whether the destination itself changes the file when it is uploaded.
Change dimensions before chasing quality
Dimensions matter as well as format. Reducing 4,000 × 3,000 pixels to 2,000 × 1,500 changes twelve million pixels to three million. This does not promise a particular file-size reduction, but removes detail a smaller display may not need.
Choose dimensions for the largest intended display and preserve the aspect ratio. Screenshots may need extra width to retain legible text. Print requirements can differ from web requirements. Avoid stretching a picture to fit a shape; make an intentional crop if the composition needs to change.
Use a short comparison routine
Make two or three exports from one original rather than endlessly lowering one slider. Record the dimensions, format and file size. Inspect each result at normal viewing size, then zoom in on the part most likely to suffer. An image-quality setting is not a percentage of visual information retained.
For a shop listing, inspect product text. For a portrait, check hair and skin texture. For a diagram, inspect fine lines and transparent edges. Keep the smallest version that still does the job, and retain the original separately for future use.
| Image type | Useful starting choice | Inspect before sending |
|---|---|---|
| Photograph | JPEG; compare accepted WebP | Texture and visible artifacts |
| Screenshot or diagram | PNG | Small text and edges |
| Transparent logo | PNG or suitable WebP | Edges on the final background |
| Restrictive upload form | Its listed supported format | Type, dimensions and size limit |
Sources & further reading
MDN — Image file type and format guide ↗Google Developers — WebP format overview ↗MDN — Canvas toBlob output formats ↗This guide is based on the sources linked above, with original explanations and examples. Software interfaces and service features can change. A documentation-based guide is not a hands-on product review. Read our editorial policy or report a correction.