📇 Exif Data

LibrePhotos reads a photo's metadata with ExifTool when it scans the photo: from the file itself and from the XMP sidecars next to it. What you change in LibrePhotos (a date, a caption, tags, a location, a rating, a rotation, the people on a photo) is stored in LibrePhotos' database. With Settings → Metadata Options → Write edits to files set to Save to sidecar or Save to media file, some of these edits are also written back, so other apps see them.

The tag names on this page are ExifTool's. A family 0 group such as XMP: matches every XMP namespace, a family 1 group such as XMP-dc: one of them. To see what a file holds, run exiftool -G1 -a -s photo.jpg. Some names differ from the EXIF standard: ExifTool calls ISO EXIF:ISO (not ISOSpeedRatings), the 35 mm focal length EXIF:FocalLengthIn35mmFormat (not FocalLengthIn35mmFilm) and the EXIF DateTime tag EXIF:ModifyDate.

info

Not released yet (comes after 1.3.0) Much of this page is new. Up to 1.3.0:

• the setting was called Synchronize metadata to disk. It wrote ratings, dates, face regions and rotations, but never captions, locations or tags, and rotations never reached a sidecar. In a HEIC, AVIF or RAW original it wrote a wrong orientation, often the opposite turn;
• a scan wrote a rating it found in a file back to disk, which in sidecar mode created an .xmp holding just that rating (harmless, unless the rating is later changed in the original by another app);
• a write always went to IMG.xmp, even next to an existing IMG.jpg.xmp, and a failed write looked like a success;
• face regions of rotated photos were written in the wrong place, adding person names replaced the photo's keywords, and deleting a face left its region in the file;
• a sidecar's date, position and camera (its exif:, tiff: and exifEX: properties) and the sidecar of a photo's RAW or video file were not read, nor were the IPTC and EXIF captions, the title, creator and copyright, the PersonInImage and HierarchicalSubject keywords, the camera and lens maker, the serial number and the other exposure fields, the altitude, and the date and camera of MKV, WebM and phone videos;
• shutter speeds faster than about 1/2000 s were stored as 0, and photos and videos turned a quarter by their orientation were stored at their unturned size (the update fixes the size);
• a photo with a sidecar was stored with the file size of the sidecar, shown in Info.

After the update, a Rescan from the Library page reads the new fields of the photos already in your library. python manage.py save_metadata --types face_tags rewrites the face regions of photos written by an older version, and python manage.py refresh_exposure_time reads just their shutter speeds again.

What LibrePhotos reads

Where a field lists several tags, the first one the photo has is used.

In LibrePhotos	Tags, best first	Notes
Date and time	XMP:DateCreated, EXIF:DateTimeOriginal, EXIF:ModifyDate, QuickTime:CreationDate, QuickTime:CreateDate, Matroska:DateTimeOriginal, Composite:GPSDateTime, then the file name	Decided by your date rules, in the order of your list; this is the default order. A date you set by hand wins over every rule. QuickTime:CreationDate is the local time a phone recorded a video at; QuickTime:CreateDate (MP4, MOV), Matroska:DateTimeOriginal (MKV, WebM) and Composite:GPSDateTime are UTC and are converted with the time zone of the photo's position, or else your default time zone. XMP:DateCreated is where LibrePhotos writes dates. Accounts created before 1.1.0 do not have its rule unless they add it with Add Rule or Reset To Defaults. Not released yet (comes after 1.3.0) Between the tags and the file name, a Google Takeout JSON next to the file gives the date.
Location	Composite:GPSLatitude, Composite:GPSLongitude	ExifTool builds them from the EXIF GPS block, the embedded XMP or a video's GPSCoordinates. The place name (city, country) is looked up from the position. Not released yet (comes after 1.3.0) A file without a position takes the one in its Google Takeout JSON, if it has one.
Altitude	Composite:GPSAltitude	In metres, negative below sea level, stored in the photo's metadata.
Rating, favorite	Rating	Without a group ExifTool answers with XMP-xmp:Rating or the EXIF Rating. A photo rated at least Minimum image rating to interpret as favorite is a favorite.
Tags	XMP:Subject, IPTC:Keywords, XMP:PersonInImage, XMP:HierarchicalSubject	All four are merged, and each keyword becomes a tag with a small file icon. Of a hierarchical keyword (Lightroom, digiKam, darktable) the last level counts: Places|USA|San Francisco adds San Francisco. The XMP-iptcExt:PersonInImage names become tags, not people: people come from face regions.
Caption	XMP:Description, XMP:Description-*, IPTC:Caption-Abstract, EXIF:ImageDescription	The description's default-language entry first, else any language entry, then the IPTC caption (older Photoshop and Lightroom, Picasa, newsroom tools), then the EXIF one. Text cameras put there, such as OLYMPUS DIGITAL CAMERA or SONY DSC, and a description that only repeats the camera model are skipped. Not released yet (comes after 1.3.0) Without any of them, the description of a Google Takeout JSON next to the file.
Title	XMP:Title, XMP:Headline, IPTC:ObjectName	Stored in the photo's metadata (/api/photos/{id}/metadata/).
Creator	XMP:Creator, IPTC:By-line, EXIF:Artist	The first name when there are several. Stored in the photo's metadata.
Copyright	XMP:Rights, IPTC:CopyrightNotice, EXIF:Copyright	Stored in the photo's metadata.
Faces and people	XMP:RegionInfo	MWG face regions (XMP-mwg-rs:RegionInfo) with normalized areas. A region with a name becomes a face of the person of that name. LibrePhotos' own face detection runs as well; a detected face that overlaps a region is the same face.
Orientation	EXIF:Orientation; for HEIC and AVIF QuickTime:Rotation and QuickTime:Mirroring	An orientation of 5 to 8 turns the photo a quarter, so its width and height are swapped. A HEIC or AVIF photo is shown under its irot and imir properties, which ExifTool reports as QuickTime:Rotation and QuickTime:Mirroring, whatever its EXIF orientation says. Face regions are placed with the same orientation.
Width, height	ImageWidth, ImageHeight; for videos also Composite:Rotation	The size the photo is shown at, used for its aspect ratio. A video recorded upright on a phone is stored landscape with a rotation of 90 or 270 degrees; its width and height are swapped.
Video length	QuickTime:Duration, Matroska:Duration	MKV and WebM files carry no QuickTime:Duration.
Camera	EXIF:Make, EXIF:Model; for videos QuickTime:Make, QuickTime:Model	Info shows the maker in front of the model ("Fujifilm X-T5"), unless the model already starts with it ("NIKON D850", not "NIKON CORPORATION NIKON D850"). Corporate words at the end of a maker's name are left out there ("OLYMPUS IMAGING CORP." shows as "OLYMPUS").
Lens	EXIF:LensMake, EXIF:LensModel	Shown like the camera.
Exposure	EXIF:FNumber, EXIF:ExposureTime, EXIF:ISO, EXIF:FocalLength, EXIF:FocalLengthIn35mmFormat	Shown in Info. The shutter speed is shown the way ExifTool prints it: 1/4000 up to a quarter second, then seconds (0.3 s, 2.5 s, 30 s).
More exposure details	EXIF:ExposureCompensation, EXIF:Flash, EXIF:MeteringMode, EXIF:WhiteBalance, EXIF:SubjectDistance, EXIF:DigitalZoomRatio	Stored in the photo's metadata; metering mode and white balance under the names ExifTool prints (Multi-segment, Auto, ...). Subject distance and digital zoom are shown under Show more in Info; 0, which EXIF uses for "unknown" and "not used", is left empty.
Camera serial number	EXIF:SerialNumber	Stored in the photo's metadata, not shown in Info.
Colour space, bit depth	EXIF:ColorSpace, File:BitsPerSample	Stored in the photo's metadata. The bit depth is read from JPEG files only.
File size	File:FileSize	Shown in Info. Read from the photo file, never from a sidecar.
Bursts	EXIF:SubSecTimeOriginal, EXIF:ImageNumber; MakerNotes:BurstMode, MakerNotes:ContinuousDrive, MakerNotes:SequenceNumber	Used by stack detection to find burst sequences. The MakerNotes tags are only read while the matching burst detection rule is on in your settings.

XMP sidecars

Which sidecars are read

A sidecar is an .xmp file next to the photo. LibrePhotos reads both naming conventions, in lower or upper case. For a photo IMG_2.jpg, from the highest priority down:

1. IMG_2.xmp, then IMG_2.XMP (Lightroom, LibrePhotos up to 1.3.0);
2. IMG_2.jpg.xmp, then IMG_2.jpg.XMP (digiKam, darktable, Immich, LibrePhotos from the next release);
3. the sidecars named after the photo's other files, such as IMG_2.CR2.xmp for the RAW file of a RAW+JPEG pair, or the video of a Live Photo;
4. other .xmp files the scan grouped with the photo;
5. the photo file itself.

Each tag is taken from the highest one that has it, so one field can come from the sidecar and the next from the photo. A keyword list in a sidecar replaces the photo's own XMP:Subject, for example, while the photo's IPTC:Keywords, which a sidecar cannot hold, are still added to the tags. On a file system that ignores case (Windows, macOS), IMG_2.xmp and IMG_2.XMP are the same file and it is read once.

Apps that leave the original untouched (geotaggers, digiKam, darktable, Lightroom) store the EXIF properties of a photo in the sidecar under XMP names. LibrePhotos reads these there:

Field	Read from the sidecar as
EXIF:DateTimeOriginal	exif:DateTimeOriginal
Composite:GPSLatitude, Composite:GPSLongitude	exif:GPSLatitude, exif:GPSLongitude
Composite:GPSDateTime	exif:GPSTimeStamp
EXIF:Make, EXIF:Model	tiff:Make, tiff:Model
EXIF:LensMake, EXIF:LensModel	exifEX:LensMake, exifEX:LensModel
EXIF:FNumber, EXIF:ExposureTime, EXIF:ISO, EXIF:FocalLength, EXIF:FocalLengthIn35mmFormat	exif:FNumber, exif:ExposureTime, exif:ISOSpeedRatings, exif:FocalLength, exif:FocalLengthIn35mmFilm
EXIF:ExposureCompensation, EXIF:MeteringMode, EXIF:WhiteBalance, EXIF:SubjectDistance, EXIF:DigitalZoomRatio	exif:ExposureBiasValue, exif:MeteringMode, exif:WhiteBalance, exif:SubjectDistance, exif:DigitalZoomRatio

The right column is how the properties are named inside the .xmp file; ExifTool shows them as XMP:DateTimeOriginal, XMP:GPSDateTime, XMP:ISO and so on. The XMP fields (rating, keywords, description, title, creator, copyright, XMP:DateCreated, face regions) are read from a sidecar under their own names. A sidecar's modify date and orientation are never read: they describe the last edit, not the photo, and a sidecar orientation must not turn LibrePhotos' thumbnails. Its flash, colour space and serial number are not read either. Nor are the tags that describe a file rather than the photo: the file size and bit depth (File: tags), and the width and height. Those always come from the photo file, even when a RAW editor's sidecar holds the size of the RAW (tiff:ImageWidth, tiff:ImageLength).

Which sidecar is written

With Write edits to files set to Save to sidecar, an edit goes to the sidecar of the photo file that already exists, so a digiKam or darktable sidecar is updated in place and keeps its other tags. When both IMG_2.xmp and IMG_2.jpg.xmp exist, the edit goes to IMG_2.xmp, the one that is read first (the backend log warns about it). When there is none, LibrePhotos creates IMG_2.jpg.xmp, which other apps also read and which cannot be mistaken for the sidecar of a RAW file next to the JPEG (IMG_2.CR2). The sidecar of a photo's RAW file (IMG_2.CR2.xmp) is read but not written: the edit goes to the sidecar of the photo's main file, the JPEG.

A photo that up to 1.3.0 got an IMG_2.xmp next to an existing IMG_2.jpg.xmp keeps both: LibrePhotos reads and writes IMG_2.xmp, and the other app keeps its own file.

Sidecars in a download

Not released yet (comes after 1.3.0) A zip download of photos also holds the XMP sidecars next to their files, so the edits saved to a sidecar travel with the photo and another app reads them from the download. That includes a sidecar LibrePhotos created after the last scan and the sidecars of a photo's RAW file. When two photos have the same file name, the second goes in as IMG_2_1.jpg and its sidecar as IMG_2_1.jpg.xmp, so each sidecar keeps the name of its file. Up to 1.3.0, a download held only the sidecars a scan had found, and none that write-back had just created.

All metadata

Not released yet. To see every tag a photo's file carries, not just the fields above, open All metadata: in the lightbox's info panel it is the link in the file row (next to the size), on the photo page the button at the end of the File card. Only the photo's owner sees it.

The dialog asks ExifTool for every tag of the media file and of each XMP sidecar the scan reads (see Which sidecars are read), one tab per file: the media file, then the sidecars, highest priority first. Tags are grouped as ExifTool groups them (IFD0, ExifIFD, GPS, the camera's maker notes, XMP-dc, QuickTime, ...), sorted by name within a group, and their values read as in ExifTool's own output (1/250, Horizontal (normal)); embedded images and other binary data show as (Binary data N bytes). The maker notes start collapsed, since they can be hundreds of tags.

• Filter tags and values narrows the list to the tags whose group, name or value contain the text, and says how many match.
• Copy as JSON copies the open tab's tags in the shape of exiftool -json -G1, ready to paste into an issue or a forum post.

The tags are read from the files when the dialog opens and are never stored; the file system details (the server's folder, file permissions) are left out, and the file is named by its path below your library folder. If the file is no longer on disk, the dialog says so: rescan its folder or put the file back. This is the quickest way to find out why a date rule picked a tag, why a sidecar value was or was not used, or which tag a camera writes a setting to.

For API clients: the photo detail response no longer carries the exif_json field, which was always empty. The tags come from GET /api/photos/{photo_id}/metadata/raw/ instead.

What LibrePhotos writes

With Off, the default, LibrePhotos never writes to your files. A scan never writes either: it only reads. With Save to sidecar or Save to media file, these edits are written after they are saved in LibrePhotos. An edit of many photos at once (a rating, Change date and time…, a location for a selection, renaming a tag) is written by a background job, so the files can lag the library by a moment.

Edit	Save to sidecar	Save to media file
Rating and favorite, also from the mobile app	XMP-xmp:Rating	XMP-xmp:Rating, and the EXIF Rating if the file has one
Date and time	XMP-photoshop:DateCreated	XMP-photoshop:DateCreated; the camera's EXIF dates stay as they are
Rotation	XMP-tiff:Orientation, for every image format	EXIF:Orientation, into JPEG, PNG, TIFF and WebP files only
Caption you type	XMP-dc:Description	XMP-dc:Description and EXIF:ImageDescription, and IPTC:Caption-Abstract if the file already has IPTC data
Location	XMP-exif:GPSLatitude, XMP-exif:GPSLongitude	In an image GPS:GPSLatitude, GPS:GPSLatitudeRef, GPS:GPSLongitude, GPS:GPSLongitudeRef; in an MP4 or MOV Keys:GPSCoordinates
Tags	XMP-dc:Subject	XMP-dc:Subject, and IPTC:Keywords if the file already has IPTC data
Faces and their names, only with Write face tags to image files	XMP-mwg-rs:RegionInfo, names added to XMP-dc:Subject	the same, in the file
Title, creator, copyright	not written	not written

Never written: the place name (city, country), which is looked up from the position again; a generated caption; albums, hidden and archived photos; and every other tag on this page. The Write edits to files options in the settings list the same edits, and the date editor, the caption and tags editors and the Pick location dialog say in a line under the editor whether the edit reaches the file, with a link to the setting.

Photos imported from Nextcloud are never written to: LibrePhotos works on a local copy, which the next scan replaces when the file changes on the server, and nothing is uploaded back. Their edits stay in LibrePhotos.

Formats

Save to sidecar works for every format, since the photo itself is never opened for writing.

Save to media file needs a format ExifTool can write: JPEG, PNG, TIFF, WebP, HEIC, AVIF, JPEG XL, GIF, MP4, MOV and most RAW formats (CR2, CR3, NEF, ARW, DNG, ORF, RAF, RW2, ...). BMP, MKV, WebM, AVI and a few RAW formats cannot be written, and an edit of such a file stays in LibrePhotos (see Writes that fail). A rotation reaches only JPEG, PNG, TIFF and WebP files, whose viewers apply an EXIF orientation. HEIC, AVIF, RAW, GIF and the other formats are not rewritten for a rotation and keep it in LibrePhotos: libheif shows a HEIC or AVIF under its irot and imir properties, and a RAW decoder ignores the tag, so a written tag would only replace the camera's own value.

Dates, rotations, captions and locations

A date is written as the local time LibrePhotos shows, without a UTC offset. Removing a date you set by hand (Remove timestamp in the date editor) removes XMP-photoshop:DateCreated again; in a media file that also removes one another app had written there.

A rotation in a sidecar is the orientation that shows the original the way LibrePhotos shows it now; for a HEIC or AVIF it starts from the file's irot and imir, not from its EXIF orientation, which can disagree. Apps that take the orientation from a sidecar, such as digiKam, show the photo turned the same way. In a media file the rotation is folded into the file's own orientation, and LibrePhotos' own rotation goes back to none, so it is not applied twice. See Rotating Photos.

A caption keeps its line breaks. Clearing the caption removes the description, and removing a location removes the position tags. Setting a location in an image file also removes the file's old altitude (GPS:GPSAltitude, GPS:GPSAltitudeRef), which belonged to the old position, and an embedded XMP-exif:GPSLatitude/GPSLongitude that would disagree with the new one. In an MP4 or MOV the older copies UserData:GPSCoordinates and ItemList:GPSCoordinates go.

Tags and keywords

Tags are written as keywords, one change at a time: adding a tag adds that keyword (once, never twice), removing it removes that keyword, and the file's other keywords stay. Renaming, merging or deleting a tag on the Albums page changes the keyword in the files of every photo that carries the tag, in one background job.

XMP:PersonInImage and XMP:HierarchicalSubject are never written. A tag that came from one of them is not written as a keyword unless you add it yourself, and removing such a tag leaves the name or the keyword path in the file. The names of people that the face write-back added stay, even when you remove a tag of the same name.

A new sidecar starts from the photo's own keywords (XMP:Subject and IPTC:Keywords), so it does not hide them. In sidecar mode a removal only reaches the sidecar: a description, position or keyword stored in the photo file itself stays there, and an app that reads the file (or a new import into LibrePhotos) sees it again. Removing the last keyword leaves the sidecar without a keyword list, so the photo file's keywords show again. Inside LibrePhotos the removal stays.

Face regions

Writing faces needs both Write face tags to image files (Settings → Face Options, off by default) and a sidecar or media file chosen under Write edits to files. Then labelling, adding, deleting or restoring a face writes the photo's regions again, as MWG regions in XMP-mwg-rs:RegionInfo with AppliedToDimensions and normalized areas. The areas are in the coordinates of the stored image, as the standard asks, so on a rotated photo (most phone portraits, and photos you turned in LibrePhotos) other apps show them on the faces.

Only faces of people you named get a name; the other faces are written as regions without one. The names are added to the keywords (XMP-dc:Subject) for Lightroom and digiKam, which show people as keywords. The photo's other keywords stay, and the name of a person no longer on the photo leaves the keywords, unless the photo has a tag of that name.

Deleting the last face removes XMP-mwg-rs:RegionInfo from the photo file; in sidecar mode the sidecar gets an empty RegionInfo instead, so the regions another app wrote into the original stay hidden. A photo that has no faces in LibrePhotos at all (not scanned for faces yet) keeps the regions of its file. XMP-MP:RegionInfoMP (Windows Photo Gallery) and XMP-digiKam:TagsList are never changed.

Writing the edits of a whole library

Not released yet (comes after 1.3.0) Write edits to files writes an edit when you make it. The edits you made before turning it on are only in LibrePhotos; Write now under the setting (Settings → Metadata Options, see Settings) writes them as a Write Metadata to Files job, with the same writes a live edit makes. Only a value that says something is written:

Kind (types)	Photos it writes
ratings	Rated 1 to 5 stars; a rating of 0 is not written.
dates	A date you set by hand.
rotations	Turned in LibrePhotos.
captions	A caption you wrote; a generated caption is never written.
locations	A position you set; a position read from the file is already there.
keywords	With tags: each tag is added to the keywords.
face_tags	With faces that are not deleted, named or not. Only with Write face tags to image files on.

A photo with none of them is not touched, so an unrated library does not get a sidecar per photo. The job writes in batches of 200 photos, each through one ExifTool process; it shows its progress in the job list, can be cancelled there, and ends with how many photos it wrote (written), left alone (skipped: a local copy of a Nextcloud photo, or the setting changed while it ran) and could not write (errors, the first 100 listed with the file and ExifTool's reason). A write it makes is LibrePhotos' own, so the next scan does not read those photos again for it (see How a rescan treats your edits).

GET /api/savemetadata/ says what it would write now (the target and a count per kind), and POST /api/savemetadata/ starts the job: {"types": [...]} picks kinds, and leaving it out writes everything your settings write. It answers 202 with the job_id, 400 while Write edits to files is Off or for a kind it does not know, and 409 while the job runs. Up to 1.3.0 it wrote the ratings of every photo, 0 included, inside the request.

python manage.py save_metadata makes the same writes for every user whose Write edits to files is on (photos of users who have it Off are skipped), with the kinds each user's settings write. --types limits the kinds, --user limits it to one user, --sidecar or --media-file overrides the setting for that one user, and --dry-run only counts.

How a rescan treats your edits

A Rescan reads every file again, and a scan reads a file again when it or its sidecar changed.

Not released yet (comes after 1.3.0) A write LibrePhotos makes itself is not such a change. A scan remembers the modification time of every file it reads and of its sidecars, and a write that ExifTool reports as done updates what was remembered, so rating or re-dating a thousand photos does not make the next scan read them all again. In media file mode the write still moves the file's modification time, so backup and sync tools see that the file changed. A change another app makes is still picked up: a file it edited, a sidecar it added or one that was deleted, before or after LibrePhotos' write. A photo indexed by an earlier version gets its times remembered on the first scan that reads it or finds it unchanged; until then, a write makes the next scan read the photo once more, as before.

What a scan does to a value you edited in LibrePhotos:

Field	On a rescan
Date and time	A date you set by hand wins over every date rule and is kept. Remove timestamp in the date editor hands the photo back to the rules.
Location	A position you set is kept. A position that came from the file follows the file: it moves when the file's position changes and is cleared when the file has none any more.
Caption	Kept. A description in the file becomes the caption only when it is new or changed since it was last imported, and only while your caption is empty or still the one imported before. A caption you cleared stays cleared.
Title, creator, copyright	Kept once you edited them through the metadata API, until you restore the photo from its file.
Tags	With Write edits to files Off, every keyword of the file becomes a tag again, so a tag you removed comes back while the file still has the keyword. With a sidecar or the media file chosen, only a keyword the file did not have before becomes a tag, such as one another app added; a tag you removed stays removed, even where the file still carries the keyword.
Rating	Taken from the file whenever the file or its sidecar has a Rating, also 0. With write-back on, that is the rating you set. With Off, a rating you changed in LibrePhotos is replaced by the file's on a rescan (#2250).
Rotation	Kept. A sidecar's orientation is never read.
Faces	The faces LibrePhotos has stay. A face region in the file that overlaps one of them is not added again.

POST /api/photos/{id}/metadata/revert-all/ restores a photo from its file: it reads the file and its sidecars again and sets every field (date, location, rating, caption, tags, title, copyright, creator) to what they say, or empties it where they say nothing. Nothing is written. In sidecar mode the sidecar holds the edits LibrePhotos wrote, so those come back as they are there.

Undoing write-back

Turning Write edits to files back to Off stops further writes; it does not change back what was written. Your edits stay in LibrePhotos either way.

Sidecar mode never changes the photo files. To take LibrePhotos' writes back, delete the sidecars it created: IMG_2.jpg.xmp, or IMG_2.xmp for writes up to 1.3.0. A sidecar that another app made and LibrePhotos updated also holds that app's data, so do not delete those blindly; remove single tags with ExifTool instead, for example exiftool -XMP-tiff:Orientation= IMG_2.jpg.xmp.

Media file mode changes your originals in place. ExifTool runs with -overwrite_original, so no IMG_2.jpg_original backup is kept; the image data itself is not re-encoded. Keep a backup before you turn it on. To see what LibrePhotos changed in a file, compare exiftool -G1 -a -s IMG_2.jpg of the file and of its backup; LibrePhotos only touches the tags in the table under What LibrePhotos writes.

Writes that fail

A write ExifTool cannot make, for example into a read-only library, a damaged file or a format that cannot hold the tag, never undoes your edit: the rating, date, caption, location, tags, face label or rotation stays in LibrePhotos. The backend log names the photo and ExifTool's reason. Labelling a face, drawing one and rotating a photo also return the reason as write_error in the API response, and the Write Metadata to Files job and manage.py save_metadata list the photos they could not write.

In the web app, a face label, a drawn face or a rotation that did not reach the file shows an orange Not written to the file notice next to the usual confirmation: "Saved in LibrePhotos, but not written to the file", followed by the reason. It stays until you close it. Changing a date, a rating, a caption, tags or a location writes the file after the edit is saved, so a failure there is only in the backend log.