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Drop images or videos, or click to uploadPNG, JPG, WebP, GIF, BMP, SVG · MP4, WebM, MOV · paste with Ctrl+V · nothing is uploaded
Drop files to start.
Set exact pixels, a percentage or a preset and resize images or short videos right in your browser. Keep the aspect ratio or crop to fit.
Exact width × height with an aspect lock, a percentage from 1 to 400 %, a longest-side limit, or 18 presets for social, web, print and avatars.
Fit inside the box, crop to fill with a nine-point anchor, force the exact size, or pad with a color or transparency.
Resize MP4, WebM and MOV clips to 9:16, 1:1 or 16:9 and get a WebM with the original audio, recorded entirely in your browser.
Files are decoded, resized and encoded on your device with the Canvas and MediaRecorder APIs. No upload, no server, works offline.
Resizing changes the number of pixels, so the question is really how the new pixels are computed. When you shrink a 4000-pixel photo to 800 pixels in one pass, each output pixel has to summarise 25 source pixels, and a naive resampler simply skips most of them. That is where jagged diagonals, shimmering textures and moiré in fabric come from. Size Converter avoids it by downscaling in steps: the image is halved repeatedly with high-quality bilinear filtering until it is within 2× of the target, then resampled once more to the exact size. Each step averages neighbouring pixels properly, so edges stay smooth and fine detail is blended instead of dropped.
Format matters as much as the resampler. Save screenshots, logos, text and anything with flat colour as PNG, which is lossless. Save photos as JPG or WebP at quality 85–92; below 80 you start to see blocks around edges. WebP is about 30 % smaller than JPG at the same quality and keeps transparency, which makes it the best choice for websites. If you need transparency and maximum compatibility, PNG is the only option.
Enlarging is different: no resizer can create detail that was never captured, so a 400-pixel image stretched to 1600 pixels will always look soft. Keep the No upscaling switch on for everyday use. When you do need to enlarge, say for a print, Pro's supersampling renders the image at twice the target size and downsamples it, which produces cleaner edges than a direct enlargement.
Most forms and platforms do not want "about this big"; they want a precise pixel box. Typical cases:
A video's resolution is the pixel size of each frame; 1920 × 1080 is 1080p, 1280 × 720 is 720p, 3840 × 2160 is 4K. The aspect ratio is the shape: 16:9 for YouTube and TV, 9:16 for Stories, Reels, Shorts and TikTok, 1:1 for feed posts and 4:5 for Instagram portrait. Converting between shapes always means cropping or padding, and this is where the Crop to fill anchor earns its keep: for a talking-head clip going from 16:9 to 9:16, set the anchor to the centre (or wherever the person is) and the subject stays in frame while the empty background is trimmed.
Bitrate is how many bits per second the encoder may spend, and it determines file size and quality far more than resolution does. Size Converter picks a bitrate proportional to the output pixel count, roughly 2.5 Mbps for 720p and 5 Mbps for 1080p, which keeps uploads small while looking clean on a phone. Because the clip plays at normal speed while it is re-recorded, a 30-second video takes about 30 seconds; keep the tab in the foreground so the browser does not throttle the frame rate.
Size Converter is a static page. Images are decoded with createImageBitmap, drawn to a canvas and encoded back by your browser; videos are played by a hidden <video> element, redrawn frame by frame and recorded with MediaRecorder. There is no upload endpoint, no account and nothing to delete afterwards. Re-encoding through the canvas also strips EXIF metadata such as GPS coordinates and camera serial numbers from photos. Your size, fit and format settings are kept in localStorage so the tool opens the way you left it.
Drop the image, choose "Exact" under Output size and type the width and height, for example 800 × 600. With the aspect lock on, typing one side fills in the other so the picture is not distorted. If the target has a different shape than the original, pick a Fit mode: "Keep ratio" fits inside the box, "Crop to fill" trims the edges, "Stretch" forces the exact size and "Pad" adds a background. Then download the result.
Downscaling keeps the image sharp when it is done well. Size Converter shrinks large images in steps (halving until close to the target) with high-quality resampling, which avoids the aliasing and jagged edges that a single-step resize produces. Upscaling cannot invent detail, so an enlarged image always looks softer; the Pro supersampling option renders at 2x and downsamples to make the result as clean as possible. Saving as PNG keeps every pixel; JPG and WebP use the quality slider (90 by default).
Yes. Size Converter decodes the video with your browser's built-in player, draws every frame onto a canvas at the new size and records the result with the MediaRecorder API, copying the audio track. Nothing is sent to a server. The output is a WebM file (VP9 or VP8 with Opus audio). Free users can convert clips up to 30 seconds at up to 720p; Pro extends this to 5 minutes and 1080p or 4K.
Browsers can record video with MediaRecorder, but almost all of them only encode to WebM (VP8/VP9) – MP4/H.264 recording is not available in a plain web page without shipping a multi-megabyte encoder. WebM plays in Chrome, Edge, Firefox, Safari 16+, Android, VLC and uploads fine to YouTube, Instagram and most social networks. If a specific app insists on MP4, open the WebM in a free converter such as HandBrake or VLC (Media → Convert) and export to H.264.
The Preset menu includes the current standards: Instagram square 1080 × 1080, Instagram portrait 1080 × 1350, Stories and Reels 1080 × 1920, YouTube thumbnail 1280 × 720, X/Twitter header 1500 × 500 and LinkedIn banner 1584 × 396, plus web widths (1920, 1600, 1200, 800, 400), print sizes (A4 and Letter at 300 dpi) and avatar/favicon squares from 512 down to 32 pixels. Use "Crop to fill" with the anchor grid so the subject stays in frame when the ratio changes.
Yes. Resizing images and short videos is free with no sign-up. Free exports carry a small "Size Converter · free" badge and "Download all" handles 10 files at a time. Files are processed entirely on your device with the Canvas and MediaRecorder APIs and never leave your computer; the tool keeps working offline once loaded. Size Converter Pro is a one-time purchase that removes the badge and unlocks unlimited batches with ZIP download, longer and larger videos, supersampled upscaling and saved size presets.
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