Compress image

Compress image re-encodes one browser-readable image with a selected quality value. Before moving the slider, identify the constraint you need to meet. An upload form may specify a hard limit such as 2 MB. A website may need a much smaller delivery budget based on page performance. An email attachment may simply need to pass a mail server limit. Those goals call for different choices, and the smallest possible file is rarely the only measure of success.

Record the original pixel dimensions and file size shown by the workbench. Leave Target size empty when the pixel dimensions must stay unchanged. When you enter a target, the tool keeps the selected quality fixed. If the full-size encoding exceeds the limit, it finds the largest proportional dimensions that fit and reports them with the result.

The browser decodes the selected file into an image, draws its full dimensions onto a canvas, and creates a new image blob. The quality slider ranges from 10 to 100 percent and starts at 82 percent. Internally, that number is passed to the canvas encoder as a value from 0.1 to 1. Processing occurs after you press Compress image. Both source and output stay inside the active page instead of being uploaded to PWRKIT for server-side compression.

The output always keeps the source format: PNG stays PNG, JPEG stays JPEG, and WebP stays WebP. The tool never presents a larger re-encoding as compression. JPEG and WebP respond directly to quality changes. PNG compression reduces color detail while preserving the PNG container and transparency.

Begin near the default rather than dropping straight to 10 percent. The estimated size updates after each slider change and comes from encoding the selected image in its original format. If a new encoding is larger, the estimate stays at the original size. Enter a target size when you need a hard limit instead of adjusting quality by trial and error.

Look closely at the content most likely to reveal compression damage. Faces can develop waxy texture. Fine hair, leaves, and fabric can lose detail. Text and interface screenshots can show halos around hard edges. Gradients can develop bands. A quality value is not a universal visual score, and two browsers may encode the same canvas differently. Keep the chosen value tied to a tested output rather than documenting it as a guarantee for every file.

JPEG is suited to photographs and other continuous-tone images. It uses lossy compression and has no transparency channel. PNG can retain transparency, which suits logos, diagrams, and interface captures with sharp edges. WebP supports lossy compression and transparency. Compress image keeps the uploaded format; use a conversion tool only when you intend to change it.

Do not judge format only by the extension. A screenshot saved as JPEG may be smaller but show ringing around text. A large photographic PNG may waste space because lossless compression must preserve every pixel value. WebP may reduce a photograph well, but a downstream publishing system can still reject it or convert it again. Confirm what the destination accepts, then compare output size and appearance. If you need a specific format regardless of the source, use the matching conversion tool instead of relying on compression's source-based selection.

Imagine a 4.8 MB JPEG from a phone that will appear 1280 pixels wide in an article. Resize a copy to 1280 pixels wide while preserving its aspect ratio, then bring that resized copy into Compress image. Start at 82 percent and process it. Open the downloaded result at its intended display size and at 100 percent. Check the subject's eyes, hair, high-contrast edges, and any text in the scene. If those areas hold up, compare the file size against the page budget.

If the result remains above budget, try a lower quality or convert the resized source to WebP and compare. Keep filenames clear so the attempts are not confused. The reported percentage compares output bytes with the selected input bytes, not with the phone original if resizing happened in a separate step. Measure the final file that will be published. After uploading it, inspect the delivered network resource because content systems and image CDNs may create their own derivatives.

The comparison preview places the original on the left and the compressed image on the right. Drag the centered divider to reveal either version. Pinch or stretch with two fingers to zoom around the pointer, then move two fingers together to pan across the image. The Download button reports the final size, and the status states whether a target was met. If the tool reduced dimensions to reach a target, the status includes the output width and height.

Download and open the result in a separate viewer. Confirm its width and height, file extension, transparency where required, orientation, and visible detail. Compare it with the original at the same zoom. A browser preview can hide flaws when an image is scaled down. Also test the actual upload or publishing path. A service may impose pixel limits, inspect MIME type, strip transparency, or recompress files. Passing the local preview is necessary, but it does not prove compatibility with every destination.

If the input is refused, check that it is an image no larger than 30 MB and that the browser can open it. A filename ending in .jpg is not enough when the bytes contain another format or corruption. Exporting a clean copy from a trusted editor often resolves a decode failure. If a large image opens but processing fails, its decoded pixel buffer may exceed available canvas memory. Resize it in desktop software or create a smaller source before trying again.

If the estimate matches the original size, a same-format re-encoding would be larger at the selected quality. Lower the quality or enter a target size. A target never lowers the selected quality; it reduces dimensions only when the full-size result is too large. Raise the quality when fine detail matters most, or remove the target to preserve the original dimensions. Reset removes the selected source and temporary result, so download any version you need first. The original file on disk is never overwritten.

Compression changes encoding and keeps pixel dimensions unless a target size requires a smaller frame. Resize image gives you direct control of width and height. Crop image removes part of the frame. Convert to JPG, PNG, or WebP selects one output format. Make structural edits before setting the final compression target.

Keep an untouched source outside the workflow. Each canvas-based operation creates a new file, and repeated lossy passes can reduce quality. For a transparent logo, PNG or WebP may be required even when JPEG would be smaller. For a photo without transparency, JPEG or WebP is usually more appropriate than PNG. For an archival master, a web compressor should not replace the original. The downloaded copy is a delivery asset whose success depends on its destination, not a universal substitute for source media.

A file-size budget should account for every image loaded on the page, not just one result. Ten acceptable 300 KB images still transfer about 3 MB before scripts, fonts, and other assets. Identify which image is the largest contributor, which appears above the fold, and which variants the browser actually requests. Local compression helps prepare assets, but page-level measurement decides whether the combined result meets the performance goal.

Compression cannot correct poor framing, excessive dimensions, or the wrong source. A tightly cropped, properly sized photograph at moderate quality often looks better than an oversized full frame pushed to a very low quality. Make structural edits before tuning the encoder. Then save the chosen output once, record its purpose, and avoid another lossy export in downstream software unless that system requires it.

For repeatable team work, test a small representative set before applying a quality rule to a library. Include a detailed photograph, a smooth gradient, a screenshot, and a transparent graphic if those subjects occur in the product. Record the browser used, target dimensions, output format, quality value, file size, and visible concerns. The observations give later editors a starting point while leaving room for image-specific judgment.

Animated sources need separate handling. The canvas processes the decoded frame it draws and the downloaded copy should not be expected to retain a source animation. The same caution applies to layered or multi-page image containers. If motion or multiple frames are required, use an encoder that explicitly supports that structure and verify the complete sequence, not only the still preview shown here.

Compression review should also include transparency when the output remains PNG or WebP. Place the downloaded asset over dark, light, and patterned backgrounds to reveal fringes or unintended opaque pixels. A reduced byte count does not compensate for a broken alpha edge. Approve the file against the background conditions it will encounter in the product.