JPG, PNG or WebP: which image format should you use?
Start with where the image will be used, then choose the format. A small file that loses a logo’s transparency or fails an upload form is not a useful optimization.
Start with the destination
Read the destination’s accepted formats, maximum pixel dimensions and file-size limit before changing anything. These are separate requirements. A form may accept JPG but reject WebP, while a website you control may allow either. Keep those requirements beside the original file so each export has a clear purpose.
Give the exported copy a recognizable name and retain the original. Do not replace a carefully edited source with the first smaller download. If a service changes uploaded images again, inspect the version it actually publishes. A local preview tells you about this export, not every later transformation or platform.
Pixels and bytes answer different questions
Pixel dimensions describe how many picture samples the image contains. Bytes describe the size of its encoded file. Reducing dimensions can help when the source is far larger than the destination needs, but changing dimensions alone does not establish the final byte size. Always inspect both measurements after processing.
For example, the Image Resizer fits a 4000 × 2000 image inside a 1200 × 1200 box as 1200 × 600. It does not stretch the picture into a square. Its PNG download may still be larger than a source JPEG, which is why the separate compressor reports actual input and output bytes.
Use a format as a starting point, not a verdict
The table narrows the choice. It does not rank formats for every image or every destination. A useful comparison exports the same source for the intended task, checks the resulting pixels and size, then confirms that the destination accepts the file. A familiar extension by itself does not prove those things.
Our compressor offers browser-encoded WebP or JPG; its quality control is an encoder setting. Quality at 80% is not a promise of 80% fewer bytes, and moving it to 100% does not establish a lossless workflow. The linked references explain the underlying formats and browser export behavior.
| Format | A useful starting task | Check before using it |
|---|---|---|
JPG / JPEG | Photographs with an opaque background | Lossy detail and the absence of alpha |
PNG | Transparent assets or crisp raster graphics | Actual bytes, especially for photographs |
WebP | Web publishing where the destination accepts it | Encoder support, appearance and alpha requirements |
Decide what happens to transparency
A transparent logo needs its edge pixels checked on the background where it will appear. The checkerboard in a preview is just a viewing aid. It is not part of the image. Try the result on both a light and dark surface if the asset will be used in both contexts.
WebP export in this compressor retains decoded alpha. JPG export instead paints a chosen solid colour behind the source, initially white. Set that colour deliberately and inspect soft edges or shadows. Changing an opaque JPG into PNG cannot recover a removed background or invent the original transparent pixels.
Inspect text, diagrams and screenshots closely
A screenshot can contain tiny type, thin rules and flat colours. Inspect those features rather than judging only the photograph-like parts of the preview. When an export is smaller, zoom in enough to notice damaged letter edges or coloured halos, then check it again at its real published size.
Keep the pixel dimensions needed for legibility. A very small byte target can conflict with readable text, and repeatedly exporting an already degraded file will not restore the source. Start each comparison from the original. If a destination requires PNG, use the appropriate converter and compare its actual size instead of assuming PNG must be smaller.
Run a controlled local comparison
Select a static PNG, JPG or WebP in Image Compressor. Begin with its WebP output, 80% quality and 1600-pixel maximum width and height. These are initial settings, not a recommendation for every asset. The image keeps its proportions and small inputs are never enlarged. Raise the bounds when the destination needs more pixels.
Process once, note the actual output size and inspect the preview. Change one setting for the next comparison so you know what caused the difference. If you choose JPG, set the background before processing. Changing any option clears the old result; download the version matching the settings you intend to use.
Keep a larger result only for a reason
Re-encoding is not guaranteed to reduce bytes. A source may already be efficient, or the new format may be a poor fit for its content. The compressor explicitly reports larger and equal outputs. A bigger result can still solve a compatibility requirement, but it should not be described as a file-size saving.
If the result is larger, first decide whether conversion is actually needed. Then try lower quality or smaller pixel bounds when the task allows it. Compare the appearance again after every meaningful change. This version does not search automatically for an exact 100 KB result, so do not treat the controls as a guaranteed upload-limit solver.
Know what the local tools leave out
The tools process selected images inside the browser tab. They do not upload image pixels to our server or call a paid AI service. The site still requests ordinary page resources. Save a result before refreshing or closing; clearing a preview does not delete a file you already downloaded to your device.
These are publishing exports, not an archival metadata workflow. Browser decoding, orientation and colour handling can affect the pixels, and source metadata is not copied. Current image inputs are limited to 20 MiB, 16 megapixels and 8192 pixels per side. Animated images are rejected instead of quietly reducing them to a single frame.
Check the published version
Before replacing a live asset, verify its filename, format, pixel dimensions, transparency and bytes. Test the real upload rather than relying on an extension rename. Open the published page at the sizes your audience uses, including a narrow mobile view. Keep a way to restore the original if the result is unsuitable.
For a site icon, use Favicon Generator to create the required package rather than assuming one ordinary image becomes a complete icon setup. For a public page’s declared sharing image, OG Image Checker can inspect the tags, but it does not certify every platform’s rendering. Image preparation and page checks answer different questions.
Frequently asked questions
Is WebP always the best choice?
No. The destination, image content, alpha needs and actual output matter. WebP is one option in our compressor, while a restrictive form may require JPG or PNG. Compare the export you will really use.
Does converting JPG to PNG improve detail?
It does not restore information lost earlier. The converter stores decoded pixels in a new format, without recreating missing detail or transparency. Keep the original source and judge whether the destination requires the conversion.
Why did compression make my file larger?
Encoding has format and content tradeoffs. The input may already be efficient, or the chosen export may not suit it. Check actual bytes and the preview; keep the original or adjust quality and dimensions if appropriate.
Can these tools guarantee a particular KB limit?
No. Pixel limits and quality are controls, not a guaranteed byte-size target. Review the actual download and test the destination. If it still exceeds a required limit, reduce suitable dimensions or quality and inspect the result again.