# Compress or trim video > Browser-only file conversion. Selected files are processed on this device and are not uploaded to a conversion server. Source: https://localconverter.tech/compress-video Create a shorter or smaller video copy by selecting a segment, maximum width and encoding quality. Choose MP4, WebM, MOV or MKV for the receiving application. This re-encodes the video rather than promising a fixed file size, so review the actual result and playback quality before sharing it. ## Useful tasks - Make a short video attachment - Reduce a clip’s frame dimensions - Export a demonstration excerpt as MP4 ## Steps 1. **Choose a supported video**: Add one video or GIF source and identify the useful section. Sources need a known duration of at most two hours and supported frame dimensions. 2. **Set the selected segment**: Enter start and length in seconds, keeping the requested length within 120 seconds. The length field describes time after start rather than an absolute end point. 3. **Choose size and quality**: Select output format, maximum width and quality. Lower quality-number values retain more detail, while a smaller width can reduce the amount of video data substantially. 4. **Encode and review playback**: Run the tool and download the result. Check motion, small text, sound and actual size, then adjust the settings if the clip remains larger than your destination allows. ## Settings - **Output format**: Choose output format according to the result you need. Available choices: MP4; WEBM; MOV; MKV. The initial selection is MP4. - **Maximum width**: Maximum width accepts values from 16 to 1920, using whole numbers. The initial value is 1280. Change it for a specific output requirement, then check the result before processing more files. - **Quality (lower = better)**: Quality (lower = better) accepts values from 16 to 45, using whole numbers. The initial value is 26. Change it for a specific output requirement, then check the result before processing more files. - **Start (seconds)**: Start (seconds) accepts values from 0 to 7200, in increments of 0.1. The initial value is 0. Change it for a specific output requirement, then check the result before processing more files. - **Length (seconds)**: Length (seconds) accepts values from 0.1 to 120, in increments of 0.1. The initial value is 20. Change it for a specific output requirement, then check the result before processing more files. ## A demonstration for an attachment A long recording contains a twenty-second demonstration starting at forty seconds. Select that segment, choose MP4 with a maximum width of 960 and quality 28. Download and play the result, checking interface readability and the actual attachment size. ## Check the result Upload a file, adjust settings and run the tool. All processing uses the local engine. Media jobs are bounded to 120 seconds; animations to 240 frames, 30 seconds and 64 million decoded pixels. Open the saved output in the app or workflow where you plan to use it. Check one representative result before repeating the same settings with more files. The original files stay unchanged. ## Limits - Files are processed on this device. Browser memory and engine-specific limits apply. Save results before reloading. - Media jobs are bounded to 120 seconds; animations to 240 frames, 30 seconds and 64 million decoded pixels. - Upload one file with a combined size of at most 100 MB. The completed output must fit within 200 MB. - Files are checked by the local engine; a matching filename alone is not proof of valid contents. - Selections and completed jobs stay available while you navigate inside this tab. Use My files to revisit results. Reloading or closing the tab clears the workspace; download results you want to keep first. ## Questions ### Is there a target file-size setting? This tool controls format, maximum width, quality and segment duration rather than a target number of KB. Actual size depends on the image content and sound, so compare the output with any destination size requirement. ### Why does a lower quality number look better? The quality field uses a constant-rate-factor style value: lower numbers request higher visual quality and usually more data. Higher values allow stronger compression, which can introduce visible artefacts in movement, fine texture or small text. ### Will maximum width enlarge a small clip? The regular video encode uses width as a ceiling and does not enlarge frames that are already smaller. Dimensions are also adjusted for compatible even pixel sizes, so inspect the final output if a destination demands exact dimensions. ### Does this remove the sound? Ordinary video compression retains an available source audio track. Use Mute video when the intended result must be silent, or Replace video audio when a different recording should accompany the selected visual segment. ### Does Compress or trim video upload files to another service? Processing runs in this browser, on your device. Files and pasted input are not uploaded to a conversion server. The website and required engine assets must load first; large operations depend on available device memory. ### Can I continue after changing pages? Selections and completed jobs stay available while you navigate inside this tab. Use My files to revisit results. Reloading or closing the tab clears the workspace; download results you want to keep first. ## Related guides - [GIF to video](https://localconverter.tech/animation-to-video.md) - [Video to animated WebP, APNG or GIF](https://localconverter.tech/video-to-animation.md) - [Extract video or GIF frames](https://localconverter.tech/extract-frames.md) - [Crop, rotate, speed or reverse video](https://localconverter.tech/transform-video.md) - [MP4 to WEBM](https://localconverter.tech/mp4-to-webm.md) - [MP4 to MOV](https://localconverter.tech/mp4-to-mov.md)