Resize Image FREE | Change Image Width and Height Online Instantly

Resize any JPG, PNG, or WebP image by entering exact pixel dimensions or a percentage. Lock the aspect ratio to prevent distortion. Preview the resized image before downloading. Runs entirely in your browser — no upload, no account.

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Image Resizer

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Frequently Asked Questions

Enable the Lock Aspect Ratio checkbox (it is on by default). When locked, changing the width automatically recalculates the height to maintain the original proportional relationship between the two dimensions. This ensures the image scales uniformly and does not appear stretched or squashed. To change both dimensions independently, uncheck the lock option.

Pixel mode lets you enter the exact output dimensions in pixels — precise control for target sizes like 1920x1080, 800x600, or 150x150 for thumbnails. Percentage mode scales the image relative to its original size — entering 50% produces an image half the original dimensions in both width and height. Percentage mode is useful when you know how much you want to scale without needing to calculate exact pixel values.

There is no enforced maximum in the tool, but very large canvas sizes (above 16384px in either dimension) may be unsupported by some browsers, particularly on mobile. Browsers may also limit total canvas memory. For practical use, stay within 8000px in either dimension for reliable results across all devices.

Reducing the pixel dimensions reduces the number of pixels in the image and therefore the file size in most cases. However, changing from PNG (lossless) to JPG (lossy) output has a much larger effect on file size than dimensional resizing alone. For the smallest file size, reduce dimensions and switch to JPG or WebP output format. Use our dedicated Image Compressor for quality-controlled file size reduction.

No. The canvas-based approach flattens animated GIFs to their first frame. Only the first frame of an animated GIF will appear in the output. For animated GIF resizing, specialist software such as GIMP, Photoshop, or an online animated GIF editor is required.

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Free Image Resizer Online — Resize Photos and Images to Any Pixel Size Instantly

Resizing images is one of the most fundamental tasks in digital content creation. Social media platforms impose strict image dimension requirements: Instagram posts work best at 1080x1080 pixels for square or 1080x1350 for portrait format; Twitter card images require 1200x628 pixels; LinkedIn article covers work at 1200x627; YouTube thumbnails require exactly 1280x720 pixels. Uploading an incorrectly sized image results in automatic cropping or pillarboxing that can cut off important content. The Image Resizer on OneDocPDF lets you enter exact pixel dimensions or a percentage scale, preview the resized result, and download it in JPG, PNG, or WebP format — entirely in your browser without uploading anything.

The aspect ratio lock is the most important feature for preventing distortion. When you resize an image by entering only a width and the height auto-calculates, or vice versa, the image scales proportionally and nothing is squashed or stretched. This is the correct behaviour for almost all photo and graphic resizing. Only uncheck the lock when you intentionally need to resize to a specific non-proportional target — for example filling an exact banner slot that has a different aspect ratio than your source image.

Percentage mode is particularly useful for batch conceptual scaling when you know how much smaller the output should be relative to the original. If you need to provide an image at half the resolution for a mobile breakpoint, entering 50% width and 50% height (with lock enabled) produces exactly that. If you need a 3x retina version of a base graphic, enter 300%. This is more intuitive than calculating target pixel values from large source dimensions.

Output format choice affects both quality and file size. PNG produces lossless output — ideal for logos, screenshots, graphics with text, and any image where pixel-perfect sharpness matters. JPG uses lossy compression but produces much smaller files — suitable for photographs where compression artefacts at high quality settings are imperceptible. WebP provides the best compression-to-quality ratio and is supported by all modern browsers, making it the best choice for web publication. For the smallest file output after resizing, see our Image Compressor which gives direct control over compression level.

Explore more image editing tools in our free suite: Crop Image to trim dimensions to a specific region, Rotate Image to correct orientation, Convert Image Format to switch between file types, and Compress Image to control file size. Browse the complete image tools collection on OneDocPDF — every tool is free, private, and browser-based.