MEDIA Format
JPEG (Joint Photographic Experts Group) is the most widely used image format for photographs and complex colour images on the web. It uses lossy compression to reduce file size by discarding image data that is less visible to the human eye. Most digital cameras produce JPEG files by default.
How JPEG compression works
JPEG divides the image into 8×8 pixel blocks and applies discrete cosine transform to represent each block as a combination of frequency components. Lower-frequency components (gradual colour transitions) are preserved with higher precision; higher-frequency components (sharp edges, fine detail) are compressed more aggressively.
The compression quality setting controls the trade-off. Quality 90 produces a file that looks nearly identical to the original at roughly 40–60% of the original size. Quality 60 produces visible compression artefacts but a much smaller file. Most web use cases work well at quality 75–85.
JPEG vs modern formats
JPEG was designed in 1992. WebP and AVIF both achieve significantly better compression at equivalent quality. A JPEG at quality 80 and a WebP at quality 80 look similar, but the WebP is 25–35% smaller. Replacing existing JPEG files with WebP or AVIF is one of the highest-impact optimisations available for most WordPress sites.
Mediapapa Pro converts JPEG files to WebP or AVIF via the Mediapapa API. The original quality level is matched or exceeded in the converted version.
Frequently asked questions
Does WordPress support JPEG by default?
Yes. JPEG is one of WordPress’s natively supported upload formats (image/jpeg). It has been supported since WordPress 1.0.
Should I stop using JPEG on my WordPress site?
New uploads can go directly to WebP if your workflow supports it. For existing libraries, Mediapapa’s bulk conversion replaces JPEG files with WebP or AVIF. The attachment ID and URL remain the same after conversion.
Related terms: WebP · AVIF · Lossy compression · Image Optimisation
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