JPEG format: how lossy photo compression works
JPEG is the standard format for photographs on the web. It uses lossy compression to reach small file sizes, which is ideal for continuous-tone images but a poor fit for sharp-edged graphics or transparency.
Reach for JPEG when you are saving photographs or realistic images and want a small file that every browser and device can open. Choose PNG or WebP instead when you need crisp edges, text, or transparency.
How JPEG lossy compression works
JPEG is a lossy format: it permanently discards some image information to make files smaller. The encoder splits the picture into small blocks, converts each block into frequency components using a discrete cosine transform, and then quantizes those components — keeping the coarse detail your eye notices most and throwing away fine detail it is less likely to see.
Because information is discarded, decoding a JPEG never reproduces the original pixels exactly. Re-saving a JPEG repeatedly compounds this loss, so it is best to keep an original and export a fresh JPEG only when you need one.
The format is defined by the ITU-T T.81 / ISO-IEC 10918 standard, which is why JPEG decoding is built into virtually every browser, operating system, and camera.
What the quality setting controls
A JPEG quality value adjusts how aggressively the quantization step discards detail. Higher quality keeps more frequency information, producing a larger, cleaner file; lower quality discards more, producing a smaller file with more visible artifacts such as blocking around edges and halos near high-contrast lines.
Quality is not a linear percentage of visible fidelity. On typical photographs, high settings look nearly indistinguishable from the source while still saving space, and the visible cost of compression grows quickly only at the lower end of the scale.
Choosing a quality level
| Quality range | Typical use | Trade-off |
|---|---|---|
| High | Archival photos, hero images | Largest files, artifacts rarely visible |
| Medium | General web photos | Good balance of size and appearance |
| Low | Thumbnails, tight bandwidth budgets | Smallest files, visible blocking and halos |
Metadata in JPEG files
JPEG files can carry metadata such as EXIF camera settings, GPS location, timestamps, and color-profile information. This data is useful for organizing a photo library but can leak private details — for example, the exact location where a photo was taken — when a file is shared publicly.
Stripping metadata reduces both privacy exposure and file size. PixMovo removes metadata by default during conversion so that shared images do not carry hidden location or device information.
Photos versus graphics
- Photographs and realistic renders compress well as JPEG because smooth gradients hide the format's rounding.
- Screenshots, logos, and diagrams with hard edges and flat colors show JPEG artifacts clearly — use PNG or WebP for these.
- Text on a solid background becomes fuzzy under JPEG compression; a lossless format keeps it sharp.
- JPEG has no transparency channel, so any image that needs a transparent background must use PNG or WebP.
Current PixMovo settings
PixMovo can convert JPEG, PNG, and WebP images to and from one another. Selecting JPEG as the target produces a standard baseline JPEG suitable for the web.
Metadata stripping is applied by default, and the same conservative format allowlist governs both uploads and targets. PixMovo does not currently export other image formats such as GIF or TIFF from the image tool.
Worked example: exporting a web photo as JPEG
- Start from the highest-quality original
Open the untouched photo — ideally a PNG export or a JPEG saved once at high quality — so you are not compressing an already-degraded file.
- Convert to JPEG in PixMovo
Upload the image and choose JPEG as the target format. PixMovo strips metadata as it converts.
- Check edges and gradients
Review the result at full size. If you see blocking around text or banding in a sky, the source may not suit JPEG — try PNG or WebP instead.
Use an image converter
Frequently asked questions
- Is JPEG lossy or lossless?
- JPEG is lossy: it discards image detail to shrink the file, so the decoded image is never a pixel-exact copy of the original.
- Does JPEG support transparency?
- No. JPEG has no alpha channel. If you need a transparent background, use PNG or WebP instead.
- Will re-saving a JPEG lower its quality?
- Yes. Each save re-applies lossy compression and compounds the loss. Keep an original and export a fresh JPEG only when needed.
- Is JPEG good for screenshots and logos?
- Not usually. Hard edges and flat colors reveal JPEG artifacts. PNG or WebP keep text and line art crisp.
- Does converting to JPEG remove my photo's location data?
- PixMovo strips metadata by default during conversion, which removes EXIF location and device information from the exported file.