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Marvin's Toolbox.

Webcam Test

Check that your camera works before a call. Pick a device and a resolution, watch a large live preview with the resolution and frame rate it really delivers, line yourself up with a framing grid, and save a snapshot.

Runs entirely in your browser. Nothing you put in here gets uploaded.

Camera

Flips the preview and snapshots
Rule of thirds lines over the preview

Camera is off

Nothing touches your camera until you press Start. Your browser asks for permission first.

Next steps

Send this tool's output straight into another tool.

Image Annotator

Draw arrows, boxes, text, highlights and numbered steps on a screenshot, blur or pixelate anything private, crop the result and add a watermark. The finished image downloads as PNG or JPG or goes straight to your clipboard.

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JPG Image Compressor

Compress images to JPEG at a target file size or quality, with presets for WhatsApp, Instagram and Discord, optional resizing and EXIF kept or stripped.

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Image Converter

Convert images between JPEG, PNG, WebP and AVIF, and open iPhone HEIC photos too. Drop in as many as you like, pick a format, and dial in the quality for the lossy ones. When you convert to JPEG, choose the colour that fills any transparency. Live previews, download one or all at once.

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EXIF Editor

See and edit the EXIF metadata inside a photo, then download it with your changes or save a copy with all metadata removed, GPS included. It reads JPEG, PNG, HEIC and more, and edits JPEG files.

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EXIF Transfer

Copy the EXIF metadata from one photo onto another without changing the destination's pixels. That covers camera model, lens, focal length, exposure, GPS and more. Choose to replace all metadata or only fill in what the source provides.

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Hash Generator

Hash text or a file with MD5, SHA-1, SHA-256, SHA-512, SHA-3, BLAKE2, BLAKE3, CRC32 and more, all computed live as you type. Compare against an expected checksum and copy any digest.

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Checksum Validator

Verify a file against its checksum. Drop the file and paste the expected hash or a sha256sum line, and the hash type is detected for you, from MD5 to BLAKE3.

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Data Compressor

Compress text or a file with gzip, deflate, brotli or Zstandard and see the size before and after, the compression ratio and how long it took. One click tries every method and recommends the smallest result.

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Data Decompressor

Decompress gzip, deflate, brotli or Zstandard data from a file or pasted Base64 and read the result as text or download it. Detects the format from the magic bytes where possible, with a manual override.

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About the Webcam Test Tool

This tool checks that your camera works before a call. Nothing touches the camera until you press Start. The preview shows the resolution the camera really delivers and a frame rate measured from the frames that arrive, not just the number the driver reports.

Switch between cameras and resolution presets, mirror the picture or lay a rule of thirds grid over it to check your framing. Save a PNG snapshot, copy it, or send it on to the Image Annotator. To check your microphone as well, use the Microphone Test.

What you can do

  • Test your webcam before a video call
  • Check the real resolution and frame rate of a webcam
  • Find out why a camera is not working
  • Compare the resolutions a webcam supports
  • Check your framing with a rule of thirds grid
  • Take a PNG snapshot from your webcam

How to use the Webcam Test

  1. 1Press Start camera and choose Allow when your browser asks.
  2. 2Pick another camera from the list if you have more than one. Cameras you plug in appear on their own.
  3. 3Try the resolution presets and read the measured frame rate next to the preview.
  4. 4Turn on the framing grid to line yourself up, and the mirror switch to see yourself the way others do.
  5. 5Take a snapshot to download, copy or forward.

When the camera will not start

The tool explains what the browser reported and what to do next. Blocked means the site or your operating system has denied access, and the fix is in the site settings next to the address bar or in the privacy settings of macOS or Windows. Busy almost always means another app or tab is holding the camera, so close video calls and other recording apps first. No device found means the browser cannot see a camera, and one you plug in afterwards shows up without a reload.

Why the measured frame rate can be lower

Cameras often report 30 fps and deliver less. In dim light many webcams lengthen the exposure, which lowers the frame rate, so more light is the first thing to try. The measurement also tops out at your display's refresh rate. If you ask for a resolution the camera cannot reach, it delivers the nearest mode it has, and the tool tells you what you got instead.

Mirrored or not

Most call apps show you a mirrored preview, because that is what a mirror looks like, while everyone else sees the picture the right way round. The mirror switch flips the preview and the snapshot, so turn it off to check that text behind you reads correctly.

When the camera switches off

The camera stops when you press Stop, leave the page or switch to another tab, so nothing keeps running in the background. Coming back never restarts it on its own.

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Subtitle Converter

Convert subtitles between SRT and VTT, shift their timing forward or backward, and fix frame rate drift to sync out-of-sync captions. Preview the parsed cues, catch format errors, and download the converted file.

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Pull the audio track out of a video as MP3, M4A, WAV, FLAC or OGG. Drop in one or more files, pick a track and bitrate, or keep the original audio untouched when the format allows it, and download the results.

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Video Compressor

Compress a video to a quality level or a target size like 10 MB, scale it down if you like, and compare the size before and after with a preview.

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