JPEG vs PNG vs WebP: A Verification-first Choice
Compare browser image outputs by transparency, content, encoding behavior, destination support, and measured results.
Start with non-negotiable requirements
Alpha transparency required: exclude JPEG; test PNG and, if accepted, WebP.
Photograph without alpha: compare JPEG and WebP at acceptable visual quality.
Text, diagrams, or UI screenshots: inspect edges in PNG and WebP rather than assuming one winner.
Unknown recipient: ask for accepted MIME types before converting.
Worked comparison: transparent logo
Use a 1200 × 800 PNG logo with transparent corners. PNG should be checked for image/png and retained alpha. This converter's JPEG path fills white and should report image/jpeg; inspect the antialiased boundary. WebP should only be downloaded when Blob.type is image/webp, then tested in the target uploader or editor.
Quality is not a percentage of retained information
The JPEG/WebP slider is a Canvas encoder hint. A value of 0.9 does not mean 90% fidelity, 90% bytes, or lossless output. Compare multiple generated files at the final display size and measure each one.
Detect encoding fallback before naming the file
Canvas serialization can return another type when the requested type is unsupported. The AIGClub tools compare the actual Blob MIME with the request and do not create a misleading .webp or .jpg download after a fallback.
Do not infer metadata, color, or animation behavior
A pixel decode-and-export path does not establish a contract for EXIF, other metadata, ICC profiles, animation, or exact color interpretation. Keep the source and use dedicated inspection when any property is a requirement.
Acceptance test for one destination
Record browser and operating environment for the test run.
Open the downloaded output and confirm MIME and intrinsic dimensions.
Inspect transparency/background, gradients, sharp edges, small text, and photo detail.
Measure bytes and upload or open the file in the actual recipient.
Keep the original and the evidence; support can change with software versions.
FAQ
About this topic
Is WebP always smaller than JPEG or PNG?
No. Content, encoder, settings, and required quality determine measured bytes; compare actual outputs.
Why does a JPEG from a transparent logo show white?
JPEG has no alpha channel, and this converter intentionally paints white before JPEG encoding. Inspect edge pixels before approval.
Can a PNG export be called lossless for the whole workflow?
Not categorically. PNG pixel encoding differs from guarantees about browser decoding, metadata, color profiles, or earlier processing.
How can I tell whether the browser really produced WebP?
Use the output summary or inspect the downloaded file's MIME; the tool exposes a download only when Blob.type matches image/webp.
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