Image Resize & Compress

Image Resize & Compress scales and re-encodes images in your browser. Use it to shrink a 4 MB iPhone photo to a 200 KB web-friendly version, or to convert formats entirely.

Three resize modes

• Fit — keep the source’s aspect ratio; output dimensions are at most the max width / max height you specify. Best for “shrink to fit a max-size” uploads.
• Fixed — output is exactly the width × height you specify. Stretches or squashes to match (uncheck “maintain aspect” to force).
• Percentage — scale by a factor; 50% halves both dimensions. Quick for batch-style halving.

Output formats

• JPEG — smallest for photos; quality slider 0.50–1.00. JPEG doesn’t support transparency, so the chosen background color fills any transparent pixels.
• PNG — lossless; preserves transparency. Use for screenshots, line art, UI.
• WebP — smaller than JPEG at equivalent quality and supports transparency. Best modern choice.

Quality slider behavior

Quality > 0.85 is usually visually indistinguishable from the source for photos; 0.70–0.85 is a sweet spot for web. PNG ignores the slider — it’s always lossless.

HEIC / iPhone photos

Drop a .heic file and the same decode pipeline as our HEIC to JPEG tool runs. On browsers that can’t decode HEIC natively, we dynamically load libheif-js (~1.5 MB one-time).

Privacy

The image never leaves your browser. All operations are local.

Tip: consistent web output

If you have a hero image template, run a fixed-width resize (e.g. 1920 × 1080) and a JPEG quality 0.75 to keep the file size predictable regardless of the source.

Common use cases

• Meeting upload limits. Shrink a multi-megabyte photo to fit an avatar, attachment, or CMS size cap by capping its longest side and re-encoding as JPEG or WebP.
• Cutting page weight. Convert bulky PNG screenshots to WebP or quality-tuned JPEG before publishing, then check the size reduction percentage before downloading.
• Standardizing thumbnails. Use Fixed mode to force a set of images to identical dimensions, such as square 800×800 product shots.
• Converting iPhone photos. Drop HEIC files straight from an iOS device and export universally readable JPEG or PNG.
• Stripping hidden metadata. Because output is re-encoded through a fresh canvas, EXIF data such as camera model and GPS coordinates does not survive, which is useful before sharing screenshots publicly.

How to use

1. Click Choose File or drag an image onto the dashed drop zone. Files up to 50 MB are accepted, including PNG, JPEG, WebP, GIF, BMP, and HEIC.
2. The Source card shows the file name, pixel dimensions, and size along with a preview.
3. Select the output format: JPEG, PNG, or WebP. For JPEG, a background color picker appears for flattening transparency, and the quality slider (0.50 to 1.00) applies to JPEG and WebP.
4. Choose a resize mode: Fit scales the image down to fit inside a maximum width and height, Fixed forces exact dimensions, and Percentage scales by a factor from 1% to 100%.
5. In Fit mode, keep Maintain aspect ratio checked to scale proportionally; uncheck it only if you intentionally want the image stretched to the box.
6. Click Convert. The result row shows a preview, the new dimensions and size, and the percentage reduction (or increase) compared with the original.
7. Click Download to save the file, named after the original with a -resized suffix, or Convert another to reset and start over.

Tips and pitfalls

Aspect ratio is where most resized images go wrong. Fit mode with the ratio lock uses the smaller of the two scale factors, so the image always lands inside your box without distortion; Fixed mode ignores the lock and will happily squash a portrait photo into a square. Percentage mode always scales both axes equally. Resampling runs through the browser’s canvas with high-quality smoothing, which produces clean downscales, but remember that enlarging never adds detail: upscaling a 400-pixel image to 4000 pixels just interpolates the same information.

DPI is a print concept, not a screen one. An image only has pixel dimensions; DPI is a metadata hint telling print software how large to render it (inches equal pixels divided by DPI). Changing a file from 72 to 300 DPI without touching pixels changes nothing on a website. Since this tool re-encodes through a canvas, such metadata is dropped from the output entirely, along with EXIF orientation, camera data, and color profiles.

Format choice matters more than quality settings. JPEG has no alpha channel, so transparent regions are flattened onto the background color you pick; choose PNG or WebP when transparency must survive. The quality slider is passed only to lossy encoders and is ignored for lossless PNG. Finally, re-encoding is not free compression: converting an already-compressed JPEG to PNG, or re-saving at maximum quality, can make the file larger, so always glance at the reduction figure before downloading.

FAQ

Are my images uploaded to a server?

No. Decoding, resampling, and re-encoding all happen locally in your browser using the Canvas API, and the result is handed back as an in-memory blob. No network request carries your image anywhere, which also makes the tool safe for confidential screenshots and documents.

Why did my transparent PNG get a solid background when converted to JPEG?

The JPEG format has no alpha channel, so transparent pixels must be flattened onto a solid color before encoding. This tool paints the background color you choose in the color picker (white by default) behind the image in that case. If you need transparency, export as PNG or WebP instead.

Why does the quality slider have no effect on PNG output?

PNG compression is lossless, so there is no quality parameter to trade against size; the encoder ignores the slider for PNG and the value is only passed to JPEG and WebP encoders. To shrink a PNG, reduce its dimensions or convert it to a lossy format.

Why is the output file sometimes larger than the original?

Re-encoding is not always a win. Converting a photograph from JPEG to PNG usually inflates the file because lossless encoding keeps camera noise, and re-saving a heavily compressed original at maximum quality also grows it. The result panel shows the size change with an up or down arrow so you can compare before downloading.

Does resizing change the DPI of my image?

Digital images have pixel dimensions, and DPI is only a metadata hint used by print software to decide physical size: inches equal pixels divided by DPI. This tool changes the pixel dimensions, and because output is produced through a fresh canvas encode, metadata such as DPI and EXIF camera data is not carried over.

Can I convert HEIC photos from an iPhone?

Yes. HEIC and HEIF files are accepted by the picker and decoded in the browser, after which you can export them as JPEG, PNG, or WebP at whatever dimensions and quality you set.