How to compress images for an upload without losing too much quality

Start with the upload requirement, not a quality number

An upload form may limit both file size and dimensions. Read its accepted formats and maximum size first. A 500 KB limit is a requirement of a hypothetical receiving website in this example, not a BZ WorkOps limit. Keep an untouched copy of the original before preparing a smaller version.

Compression can reduce fine detail. Text, faces and product edges deserve a closer check than a soft background. A lower quality slider value does not promise a particular file size, and two pictures at the same setting can produce different sizes.

Choose a format that fits the picture

JPEG is useful for photographs when transparency is unnecessary. WebP supports photographic compression and transparency, but the receiving website must accept it. PNG preserves transparency with lossless encoding; the quality slider does not make PNG lossy. For sharp screenshots, diagrams or text, compare a PNG with a JPEG or WebP rather than choosing by extension alone.

BZ WorkOps accepts JPEG, PNG and WebP within the limits displayed by the tool. Its output is re-encoded in your browser. JPEG replaces transparent pixels with the background color you choose. Re-encoding removes most metadata and retains only the first frame of an animated input. It does not preserve a camera original or a layered design file.

Make one change at a time

1. Open Image Compressor and add one supported image. Check its original dimensions and file size in the file list.
2. Set a maximum width appropriate for the destination. Reducing a large photo can save more space than lowering quality alone. The compressor keeps proportions and does not enlarge a smaller image.
3. Select a format the receiving site accepts. For JPEG or WebP, start at a moderate quality setting and process the image.
4. Compare the reported output size with the original and the upload limit. Open the download at its actual viewing size to inspect text, edges and faces.
5. If it is still too large, try a smaller width or lower quality on the original input. If the result looks poor, raise quality or choose another format. Keep the smallest version that still meets your visual needs.

Example: prepare a product photo for a catalog

Suppose your source photo is 2,400 × 1,600 pixels and the catalog displays images at 1,200 pixels wide. A maximum width of 1,200 produces 1,200 × 800 pixels while keeping the 3:2 aspect ratio. That leaves one quarter as many pixels: 960,000 instead of 3,840,000. The byte size will not necessarily fall by the same fraction.

Try JPEG at 80% quality, download it, and compare its actual size with the receiving site’s limit. Inspect the product label and small details. If the JPEG is already below the limit and looks clear, another compression pass has little benefit. If transparency is essential, try WebP or PNG and confirm the background remains correct.

When the result gets bigger or looks worse

An input may already be encoded efficiently. Converting a JPEG photograph to PNG can increase its byte size even after resizing. A compressed file can also lose detail that cannot be recovered by raising quality later. Restart from the original rather than repeatedly compressing previous downloads.

If processing fails, try one smaller image and check the displayed file, batch and megapixel limits. Browser memory and codec support matter as well as file size. The tool estimates no guaranteed quality score; your own inspection at the intended display size is the final check.