Source: https://mactoolbox.app/glossary

# Mac glossary

File formats, codecs and Mac terms in plain English, with the Toolbox tools that work with them.

## Terms A to Z

- [**Alpha channel**: An alpha channel stores transparency in an image. Learn which formats support it and how to get a transparent background on a Mac.](https://mactoolbox.app/glossary/alpha-channel)
- [**Aspect ratio**: Aspect ratio is the ratio of width to height. Learn common ratios such as 16:9 and how to resize without stretching on a Mac.](https://mactoolbox.app/glossary/aspect-ratio)
- [**Bitrate**: Bitrate is how much data a video or audio file uses per second. See how it affects quality and file size and how to check it on a Mac.](https://mactoolbox.app/glossary/bitrate)
- [**Checksum and hash**: A checksum, or hash, is a short fingerprint of a file. Learn how to verify a download with SHA-256 on your Mac.](https://mactoolbox.app/glossary/checksum)
- [**Codec**: A codec is the method used to compress and decompress audio or video. Learn how codecs differ from file formats and how to see yours on a Mac.](https://mactoolbox.app/glossary/codec)
- [**Compression ratio**: Compression ratio compares original and compressed file sizes. Learn how to read it and how to see how much a file shrank on your Mac.](https://mactoolbox.app/glossary/compression-ratio)
- [**Container format**: A container format, such as MP4 or MOV, holds video, audio and subtitles in one file. Learn how it differs from a codec and how to change it on Mac.](https://mactoolbox.app/glossary/container-format)
- [**DPI and PPI**: DPI and PPI describe image detail per inch. Learn the difference, why 300 matters for print and how it relates to pixel size on a Mac.](https://mactoolbox.app/glossary/dpi-ppi)
- [**EXIF metadata**: EXIF is information stored inside a photo, such as camera, date and GPS location. See how to view it on a Mac and remove it before sharing.](https://mactoolbox.app/glossary/exif-metadata)
- [**FFmpeg**: FFmpeg is a free, open-source tool for converting and processing audio and video. Learn what it does and how Toolbox uses it on your Mac.](https://mactoolbox.app/glossary/ffmpeg)
- [**FLAC**: FLAC is a lossless audio format about half the size of WAV. See how it compares with MP3 and how to convert FLAC on a Mac.](https://mactoolbox.app/glossary/flac)
- [**Frame rate**: Frame rate is how many pictures per second a video shows. Learn what 24, 30 and 60 fps mean and how to check them on a Mac.](https://mactoolbox.app/glossary/frame-rate)
- [**Gatekeeper**: Gatekeeper is the macOS security feature that checks downloaded apps before they open. Learn how it works and how to see its decision for an app.](https://mactoolbox.app/glossary/gatekeeper)
- [**GIF**: GIF is an old image format used for short looping animations. Learn its limits and how to make a small GIF from a video on your Mac.](https://mactoolbox.app/glossary/gif)
- [**H.264**: H.264 is the most widely supported video codec. Learn what it does, how it compares with HEVC and how to use it when compressing video on a Mac.](https://mactoolbox.app/glossary/h264)
- [**HEIC**: HEIC is the photo format iPhones use by default. Learn what it is, how to open it on a Mac and how to convert it to JPG with Toolbox.](https://mactoolbox.app/glossary/heic)
- [**HEVC (H.265)**: HEVC, also called H.265, is a video codec that makes files about half the size of H.264 at similar quality. See where it plays and how to use it on Mac.](https://mactoolbox.app/glossary/hevc-h265)
- [**JPEG**: JPEG is the most common photo format. Learn how its lossy compression works and how to make smaller JPEGs on your Mac.](https://mactoolbox.app/glossary/jpeg)
- [**Lossless vs lossy**: Lossy compression discards detail to save space, lossless keeps everything. Learn which formats are which and how to choose on a Mac.](https://mactoolbox.app/glossary/lossless-vs-lossy)
- [**MP3**: MP3 is a lossy audio format that plays almost everywhere. Learn how bitrate affects it and how to convert audio to MP3 on a Mac.](https://mactoolbox.app/glossary/mp3)
- [**Notarization**: Notarization is Apple's automated check of Mac software outside the App Store. See what it covers and how it relates to Gatekeeper and damaged-app warnings.](https://mactoolbox.app/glossary/notarization)
- [**OCR**: OCR, or optical character recognition, turns pictures of text into real text you can search and copy. See how it works on Mac and in Toolbox.](https://mactoolbox.app/glossary/ocr)
- [**PNG**: PNG is a lossless image format with transparency. See when to use it instead of JPEG and how Toolbox saves PNGs on a Mac.](https://mactoolbox.app/glossary/png)
- [**Quarantine attribute**: The quarantine attribute is a flag macOS adds to downloaded files. See what com.apple.quarantine does and how to view or remove it.](https://mactoolbox.app/glossary/quarantine-attribute)
- [**Sample rate**: Sample rate is how many times per second audio is measured. Learn what 44.1 kHz and 48 kHz mean and how to check yours on a Mac.](https://mactoolbox.app/glossary/sample-rate)
- [**System Data**: System Data is the Storage category for space macOS cannot sort elsewhere. Learn what is in it and how to find what takes up the room.](https://mactoolbox.app/glossary/system-data)
- [**Vector vs raster**: Raster images are grids of pixels, vector images are shapes defined by math. Learn how each behaves when resized and which Mac apps use them.](https://mactoolbox.app/glossary/vector-vs-raster)
- [**WebP**: WebP is an image format for the web that makes small files and supports transparency. See how to open it and make it on a Mac.](https://mactoolbox.app/glossary/webp)