Key takeaways
- Use PNG when exact pixels or transparency matter, JPG for broadly compatible photographs, and WebP for efficient modern web delivery.
- Resizing oversized dimensions often saves more bytes than repeatedly lowering quality.
- Keep an original master because lossy conversion permanently discards image information.
PNG, JPG, and WebP can all display a photograph in a browser, but they solve different problems. Choosing by filename alone leads to predictable mistakes: transparent logos acquire a solid background, screenshots become blurry, or a four-thousand-pixel photograph is compressed repeatedly while remaining unnecessarily large.
The right choice starts with the image content and where the result will be used.
Quick decision table
| Situation | Practical choice | Why |
|---|---|---|
| Logo or icon with transparency | PNG or WebP | Both can preserve an alpha channel. |
| Photograph for broad compatibility | JPG | Nearly universal support and efficient photographic compression. |
| Photograph for a modern website | WebP | Usually provides a smaller delivery file at comparable visual quality. |
| Screenshot containing small text | PNG | Lossless storage keeps sharp edges and repeated colors clean. |
| Screenshot where size matters more than exact pixels | WebP | Can reduce size substantially, but inspect text and UI edges. |
| File that will be edited repeatedly | PNG or the original source | Repeated lossy exports accumulate artifacts. |
PNG: exact pixels and transparency
PNG uses lossless compression. Saving the same pixel data does not introduce the block artifacts associated with lossy image formats. It is a strong choice for interface screenshots, diagrams, line art, and assets with transparent areas.
Lossless does not mean small. A high-resolution camera image stored as PNG can be much larger than a visually similar JPG or WebP. PNG is most efficient when large areas repeat the same colors; it is less efficient for photographic noise and subtle gradients.
Do not convert a JPG photograph to PNG expecting lost detail to return. The conversion can make the file larger, but it cannot reconstruct information discarded by the earlier JPG encoding.
JPG: practical photographic compatibility
JPG is designed for continuous-tone images such as photographs. Its quality control trades detail for a smaller file. At sensible settings, the change can be difficult to notice at normal viewing size. At aggressive settings, halos, blocks, color smearing, and damaged text become visible.
JPG does not support transparency. PNG to JPG therefore asks for a background color and deliberately flattens transparent pixels onto it. White is appropriate for many documents, but a website asset may need the actual page background to avoid a visible rectangle.
Use JPG when the destination demands it, when compatibility is the main concern, or when a photographic image does not need transparency.
WebP: efficient web delivery
WebP supports both lossy and lossless compression as well as transparency. For current browsers it is an effective delivery format, especially for photographs and large page illustrations. JPG to WebP lets you compare the resulting dimensions and size locally before downloading.
The qualification is “delivery format.” Some older applications, document systems, email workflows, or upload portals still prescribe JPG or PNG. Check the actual destination instead of assuming browser support guarantees acceptance everywhere.
Resize before chasing quality
Pixel dimensions are often the largest source of waste. A 4000×3000 photograph contains twelve million pixels even when displayed at 800 pixels wide. Use Image Resize to create dimensions appropriate for the destination, then choose format and quality.
A practical workflow is:
- Keep the original file as the master.
- Determine the largest display or print dimensions required.
- Resize once from the master.
- Export to the intended delivery format.
- Inspect the result at 100% and at its real display size.
- Compare file size only after visual acceptance.
Avoid repeatedly opening and saving a JPG. Each lossy generation can discard more information. Return to the original for every new output size.
What “quality 80” actually means
Quality controls are encoder-specific scales, not percentages of detail retained. A value of 80 in one application is not guaranteed to match 80 in another, and it does not mean that 20% of the image was removed. Treat the value as a starting point for comparison.
Image Compress provides a before-and-after preview and size measurement. Check faces, text, high-contrast edges, gradients, and fine textures because those areas reveal compression damage first.
Privacy and metadata
Browser canvas conversion normally creates a new raster output rather than deliberately copying all source metadata. That can reduce incidental metadata transfer, but it should not be treated as a forensic sanitization guarantee across every browser and format. For sensitive publication, verify the downloaded file with a dedicated metadata inspector.
The safest general policy is simple: preserve the master privately, create a purpose-sized delivery copy, inspect that copy, and share only the result intended for the recipient.