Metadata Formats

🔍 Understanding Metadata Formats (EXIF / IPTC / XMP)

ExifPlus reads and writes multiple metadata standards. This page explains what each format is, common fields you will see, and typical use-cases.

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1) EXIF (Exchangeable Image File Format)

What it is:
EXIF is metadata embedded by cameras and smartphones into image files. It stores technical and capture information.

Common EXIF fields:

• DateTimeOriginal — when the photo was taken
• Make / Model — camera manufacturer and model
• Orientation — rotation / orientation
• FocalLength, Aperture, ExposureTime, ISO
• GPSLatitude, GPSLongitude, GPSAltitude — location data (if enabled on device)

Use-cases:

• Photographers checking exposure / lens data
• Geolocation / mapping from photo GPS
• Forensics & timeline creation

Notes:

• EXIF is image-format-specific (JPEG, TIFF, some HEIC variants).
• Many online platforms strip EXIF (for privacy).

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2) IPTC (International Press Telecommunications Council)

What it is:
IPTC is used mainly in journalism and publishing. Focuses on descriptive and rights information.

Common IPTC fields:

• Title
• Byline / Credit
• Caption / Headline
• Keywords
• DateCreated

Use-cases:

• News agencies, photo editors, content management
• Embedding rights and credit information

Notes:

• IPTC often co-exists with EXIF; some cameras/apps allow editing IPTC directly.

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3) XMP (Extensible Metadata Platform)

What it is:
XMP is a flexible XML-based metadata format introduced by Adobe. It can store structured metadata, can be embedded or sidecar.

Common XMP areas:

• Dublin Core (title, creator, description)
• IPTC Core subset (for compatibility)
• Custom namespaces (software, app-specific data)

Use-cases:

• Complex metadata needs (creative workflows)
• Interoperability across Adobe products and other tools

Notes:

• XMP is preferred for advanced workflows and can store longer or structured values.
• Many programs maintain both EXIF/IPTC and XMP copies; changes may need syncing.

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4) Video metadata (hachoir / container metadata)

What it is:
Video files (MP4/MKV/MOV) store metadata in container formats; hachoir extracts container-level metadata like duration, codecs, bitrates.

Common fields:

• Duration
• Video/Audio codec
• Bitrate
• Frame rate
• Creation date (if present)
• Streams info (resolution, channels)

Use-cases:

• Quick technical overview for submissions
• Forensic timeline from embedded timestamps

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5) Privacy & Stripping

Why metadata disappears on the web:

• CDNs and image hosting services often strip EXIF/IPTC/XMP to save space or protect privacy.
• Resizing/thumbnailing pipelines commonly remove metadata.

If you need original metadata:

• Upload original file (no resizing) or download from the original uploader account.
• Avoid using thumbnails or CDN-served resized images.

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6) Best practices when editing metadata

• Always keep a backup of original files before overwriting metadata.
• Prefer sidecar files (XMP sidecar) for non-destructive workflows if supported.
• Use canonical keys (standard EXIF/IPTC/XMP tags) rather than custom keys when possible.

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7) Resources

• EXIF spec: https://www.exif.org/
• IPTC Photo Metadata: https://iptc.org/standards/photo-metadata/
• XMP: https://www.adobe.com/devnet/xmp.html