Does Compressing a File Remove Its Metadata?

The image and video rows are the same source files throughout, where survival means all 9 GPS tags. The PDF row means its 10 Document Info keys and 13 XMP tags.

Two of those deserve a second look. sips, the tool already on your Mac, made the file 20.6% larger at quality 75 and then added metadata: IPTC went from 7 tags to 14 and XMP from 7 to 13, with a Photoshop resource block appearing out of nowhere. It is the only tool tested that finished with more metadata than it started with.

And zipping does nothing. The file that came out of the archive was byte-for-byte identical to the one that went in, all 39 EXIF tags present. Archive compression operates on the file as an opaque blob. It has no idea what an EXIF tag is.

Because metadata stripping is a decision each encoder makes independently, and most of them decided to preserve. The reasoning is sound from where they sit: an ICC profile affects how the image renders, a copyright line is somebody’s legal position, and an orientation tag decides whether the photo appears sideways. Throwing those away by default breaks more workflows than it protects.

libwebp went the other way. cwebp drops everything unless you ask for it, which is why the same image came out at 26,254 bytes with no metadata and 34,292 bytes with it. The metadata is 8,038 bytes, which is 23% of the file that keeps it. For a format built for the web, dropping it by default was the right call.

The practical consequence is that you cannot reason about this from the word “compress”. Whether your GPS coordinates survive depends on which library your tool shells out to and which flags it passes, and neither of those is usually visible in the interface.

Ours does, so here it is in full. These defaults are quoted from the settings the app itself reports back with every job, not from a manual.

The honest explanation is that these are four different pipelines with four different encoders behind them, and the default in each case is whatever that encoder does. On the JPEG path the setting does not even change the outcome: with metadata stripping explicitly switched off, the output was 90,930 bytes with zero EXIF, GPS, IPTC, XMP or ICC tags and only the four-tag JFIF header restored. An 18-byte difference.

Switch the output to WebP with the same setting and all 39 EXIF, 9 GPS, 7 XMP and 25 ICC tags come through. That file was byte-identical to ImageMagick’s own WebP output, SHA-256 and all, which is the whole explanation: on that path the app is ImageMagick, and ImageMagick preserves.

The default that catches people out is not the metadata one. Image compression also defaults to resizing: maxWidth and maxHeight of 2,000 and quality 75. The 4,032 × 3,024 test image came out at 2,000 × 1,500. That is a sensible default for sharing and the wrong one for archiving.

No, in every tool we have measured, and PDFs are where this matters most because the tags carry names rather than coordinates.

Our Tiny preset took the test contract from 162,058 to 57,377 bytes, a 64.6% reduction, and kept all 10 Document Info keys, all 13 XMP tags, all three comment author names and the embedded attachment. Medium landed at 74,008 bytes with the same result. Ghostscript took the same file to 139,864 bytes and copied Author, Title, Subject, Keywords and Creator across unchanged, replacing only the Producer string with its own.

There is one thing compression does remove, and it is the opposite of what you would guess. Rebuilding the file collapses its incremental-update history, so the previous versions of the metadata are gone even though the current version is not. Stripping does the inverse: it clears the current tags and leaves the history recoverable. That is why cleaning a PDF properly takes two commands.

No. A phone video carries coordinates in the same way a photo does, and re-encoding it copies them into the new file.

Our test clip went through ffmpeg with libx264 at CRF 28, coming out 14.8% smaller at 100,492 bytes, and still reported its title, artist, comment, GPS position and the full shooting-location record. Our own video compression produced 117,808 bytes with exactly the same tags intact.

The flag that actually removes them:

ffmpeg -i clip.mp4 -map_metadata -1 -c copy clean.mp4

That left nothing but ffmpeg’s own encoder string, at 117,713 bytes, with no re-encode and therefore no quality loss. exiftool -all= clip.mp4 also works and leaves a container creation date behind in the movie header.

One command, before and after, on whichever tool you actually use:

exiftool -a -G1 -GPSLatitude -GPSLongitude -SerialNumber \
  -DateTimeOriginal -Artist before.jpg after.jpg

Anything that prints on the “after” side survived. Do this once per tool rather than once per file; the behavior is a property of the encoder and its settings, not of the photograph.

For a folder, exiftool -r -if '$gpslatitude' -p '$filename' dir/ lists every file that still has coordinates. More of these in our exiftool reference for macOS.

The rule of thumb that survives all of this: if you need the metadata gone, remove it explicitly. Compression is not a privacy operation and no tool has promised that it is.

If your question is only “how do I get the metadata off this file”, the answer is exiftool -all= file.jpg. Free, four seconds, and the output is byte-identical to what our strip operation produces, because our strip operation is exiftool with a bundled binary. On a folder, one exiftool process is several times faster than we are.

We are also the wrong tool if you want metadata preserved through compression on the JPEG path, which is a real requirement for photographers who need their copyright line to survive. Switching our metadata setting off did not bring EXIF back on that path. ImageMagick with no flags at all does exactly what you want: 76,498 bytes with all 39 EXIF tags intact.

Where a drop target is the right shape:

• You want smaller and cleaner in one pass, without running two tools over the same folder.
• You want the original left alone automatically rather than remembering an overwrite flag.
• Someone else has to do this repeatedly and will not be installing Homebrew.

Smol is $29 once. If you are here because you are about to post photos publicly, the more useful page is our checklist for sharing photos safely, and if you want to know what these tags are before deciding, what EXIF data actually contains walks a real tag dump line by line.