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Jellyfin does not normally duplicate your movie and episode files. It reads those originals from the filesystem, then maintains separate server data: a library database, configuration, cache, logs, web-client files, metadata, artwork, subtitles, chapter images, trickplay data, segment information, and temporary transcoded output. These items can consume substantial space and should be planned and backed up separately from the media library.
The two storage categories every Jellyfin administrator should separate
Jellyfin’s source media and its server data have different purposes and different failure consequences.
Original movies and shows
Jellyfin is designed to read video and audio directly from the filesystem. Your MKV, MP4, AVI, and other source files remain the library originals. Scanning a library does not inherently create a second full copy of every movie or episode. The media can live on local disks or an attached filesystem that the Jellyfin process can read, subject to the permissions and reliability of that storage.
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Jellyfin’s server data
Server data describes, indexes, enhances, and serves the originals. It can be rebuilt in some cases, but rebuilding may take considerable time and can discard custom edits. The following roles are distinct even when an installation places them under a common parent directory.
| Data type | What it contains | Why it matters |
|---|---|---|
| Library database | Items, paths, identifiers, playback state, indexes, and other structured library information | Required for the server to retain its catalog and settings efficiently |
| Configuration | Server options, users, libraries, networking choices, and enabled features | Needed to reproduce the server’s behavior |
| Metadata and artwork | Downloaded or generated descriptions, ratings, posters, backdrops, logos, and related files | Controls how titles appear and how quickly a library can be restored |
| Cache | Cached responses and other regenerable data | Can improve responsiveness but may grow and is usually less critical than the database |
| Web-client files | Built files used when the server hosts Jellyfin’s web interface | Deployment-dependent; not every installation uses the same web directory |
| Logs | Operational and diagnostic records | Useful for troubleshooting, but they can grow if errors repeat |
| Subtitles and trickplay | Downloaded or extracted subtitle files and seek-preview data | Optional content that can improve playback and browsing |
| Transcode output | Temporary segments or files produced for a particular playback session | Can require large amounts of short-term free space |
Where Jellyfin keeps its database, configuration, cache, and logs
The default library database is a SQLite file named jellyfin.db in Jellyfin’s data directory. The project’s storage guidance says this database should be kept locally rather than on network storage. SQLite performance and locking behavior make a low-latency local disk a safer default than a remote share.
Jellyfin uses separate directory roles for data, configuration, cache, web files, and logs. Their actual locations vary with the operating system, package, container image, service account, and administrator’s settings. Command-line switches and environment variables can override defaults, so a path copied from one installation is not a universal path for another.
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How to identify the real paths on your server
- Check the service, package, or container definition that starts Jellyfin; it may map host directories into the application.
- Inspect the server’s configured data, configuration, cache, web, and log locations rather than inferring them from the media-library path.
- Measure each location separately. A nearly full transcode volume has a different remedy from a damaged database volume.
- Record the paths in your backup documentation so a restore does not omit an apparently unrelated directory.
Custom database options are advanced configuration rather than a stable API. If you relocate the database, treat the change as an installation-specific administration decision and verify it against the documentation for your Jellyfin version.
How metadata and artwork are selected
Jellyfin can obtain title information and images from remote metadata providers, from local files, or from both. Local NFO metadata is always fetched and takes priority over remote metadata providers such as TMDb. This means an NFO file can preserve your chosen title, sort name, synopsis, release information, ratings, or other fields even when a provider later changes its response.
Artwork precedence
Artwork references in an NFO file—whether a local path or a URL—take priority over artwork returned by remote providers and over images found in the media folders. A locally selected poster therefore remains authoritative until you change or remove that local reference. If the displayed image is unexpected, inspect the NFO and its referenced artwork before repeatedly refreshing remote metadata.
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Where metadata files may appear
Depending on library settings, Jellyfin may write NFO files and image files alongside the media or keep generated metadata in its metadata directory. These are separate from the SQLite database: the database indexes and relates information, while NFO and image files can act as portable, human-readable or directly usable library assets. Whether local files are written, and exactly where, is controlled by the library and deployment configuration.
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Because local NFO data has precedence, deleting or editing an NFO can change the result of a future refresh. Make such edits deliberately and include the files in backups if preserving your manual curation matters.
Chapter images are previews, not chapter markers
Chapter images are generated preview pictures associated with video chapters and stored in Jellyfin’s metadata directory. They are a type of video metadata, not replacement video files.
A chapter marker is the time position and label that lets a client jump to a chapter. A chapter image is the thumbnail shown for that position. Markers can still be displayed when chapter-image extraction is disabled. Enabling image extraction adds work during scans: Jellyfin must seek through video, decode frames, and write preview images. Large libraries can therefore take longer to scan and consume more metadata storage.
If scan time or metadata growth is a problem, decide whether visual chapter previews are worth the additional computation and disk use. Disabling them does not necessarily remove chapter markers supplied by the media or other metadata.
Segment metadata adds another layer of playback information
Jellyfin documentation for version 10.10 and later describes segment metadata that can label intervals such as intro, commercial, recap, outro, preview, or other available types. Plugins provide the segment information; compatible clients decide whether to display it or take an action such as skipping.
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Segment metadata is therefore neither a duplicate movie nor a transcode. It is descriptive data attached to time ranges in an existing media item. Its usefulness depends on both the plugin that supplies it and the client that understands it.
Subtitles and trickplay files can be optional but sizeable
Subtitles may be downloaded from a provider or extracted from the media. They can be retained as separate files and may be included in a server backup. Trickplay data consists of seek-preview information that lets a client show a strip of thumbnails while scrubbing. It may be stored outside the media tree, depending on the installation.
Neither feature is required for Jellyfin to retain the original video. They are quality-of-use data: omitting them from a backup saves space but means they may need to be regenerated or downloaded after a restore.
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Why the transcode folder becomes so large
A transcode is playback output generated for a particular client and set of constraints. It is not a replacement copy of your movie or episode and does not mean Jellyfin has duplicated the library permanently.
The client helps determine the output
When playback starts, the client sends one or more transcoding profiles describing capabilities and limits, including supported codecs, resolutions, bitrate, and additional constraints. Jellyfin uses that information, together with the source media and the playback request, to decide whether direct play, remuxing, or full transcoding is appropriate.
A device that cannot decode the source codec, a connection that cannot sustain the source bitrate, an incompatible subtitle format, or a requested resolution can all cause transcoding. Different viewers and devices can therefore create very different temporary files from the same source.
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Transcode size depends on bitrate and duration
The project’s storage documentation gives planning examples rather than guarantees. It says a transcoding folder typically needs about as much space as the original media when transcoding at an equivalent bitrate. A 50 GB Blu-ray remux might produce roughly 60 GB of transcode output at one bitrate or roughly 15 GB at another. The selected output bitrate, codec, resolution, audio handling, and session duration determine the result.
| Planning case | Illustrative space from Jellyfin documentation | Qualification |
|---|---|---|
| Moderate-sized library database | About 10–100 GB | Broad project estimate; not a rule for every small or large library |
| 50 GB Blu-ray remux, higher-output example | About 60 GB | Illustrative transcode result at a particular bitrate |
| 50 GB Blu-ray remux, lower-output example | About 15 GB | Illustrative result at a different bitrate |
| Equivalent-bitrate transcoding | Approximately the source media’s size | Typical planning guidance, not a per-session guarantee |
Temporary does not mean harmless
Transcode output is temporary, but a full disk can still stop a session or affect other services. The transcode directory is configurable, so place it on storage with enough free capacity and monitor it during simultaneous sessions. Avoid assuming that a small source file guarantees a small output: a long video, multiple audio tracks, or several concurrent users can change the requirement.
Storage planning by role
Plan capacity and performance separately for the media dataset, server data, and transcode scratch space.
- Media: prioritize capacity, sequential throughput, redundancy, and a filesystem the server can reliably access.
- Database and configuration: prioritize low latency, local placement, and reliable backups. The database should not be treated like disposable cache data.
- Metadata and artwork: allow for posters, backdrops, NFO files, chapter images, subtitles, and trickplay. Growth follows library size and enabled features.
- Transcodes: prioritize free-space headroom and sustained write performance. This area can expand rapidly during concurrent playback and then contract when sessions end.
- Cache and logs: monitor growth and rotate or clear them using supported administrative methods rather than deleting active files blindly.
A solid-state drive can be useful for server data when database responsiveness, scan time, or transcode performance is a demonstrated bottleneck. It is not a universal Jellyfin requirement, and the documentation does not justify choosing one particular drive model for every server.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Platform-specific cautions: ZFS and TrueNAS SCALE
ZFS
Jellyfin’s storage guidance gives ZFS-specific recommendations for using different record sizes for the SQLite database dataset and for large media datasets. It also warns against placing server data other than media on ZFS-formatted mechanical drives because of performance concerns. These are ZFS and workload considerations, not universal rules for every filesystem or disk type; verify the current guidance before changing dataset properties.
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The TrueNAS SCALE guide describes separate locations for configuration, cache, and transcoding, and recommends SSD storage for configuration and cache. It warns that RAM-backed transcode storage can run out of space and cause a transcode to fail. RAM disks can be fast, but their fixed size and volatility make them unsuitable when sessions may exceed the reserved capacity.
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What to back up, and what can be rebuilt
Back up the database and configuration if you want to preserve users, libraries, settings, watched status, and the server’s catalog. Include metadata and artwork when manual curation or faster recovery matters. Select subtitles and trickplay in the built-in backup facility when those generated assets are important to your household.
- Back up the Jellyfin database and configuration on a schedule appropriate to how often your library changes.
- Include selected metadata, artwork, subtitles, and trickplay rather than assuming all generated content is disposable.
- Back up original movies and shows separately according to your storage and redundancy plan; a server-data backup is not a media backup.
- Keep at least one backup independent of the live server so disk failure, accidental deletion, or a bad configuration change does not affect every copy.
- Test a restore. A backup that cannot be opened or whose paths no longer exist is not a complete recovery plan.
Transcode files are generally session output and are normally the least valuable items to preserve. Rebuilding them is preferable to spending backup capacity on temporary data, provided the transcode location will have sufficient free space when playback resumes.
Common storage problems and the right response
“My media folder did not double in size, but the server uses much more disk.”
Measure the database, metadata, cache, logs, web files, and transcode locations independently. Artwork, chapter images, subtitles, trickplay, and transcode sessions can all grow outside the media tree.
“A refresh keeps restoring the wrong poster or title.”
Inspect local NFO files and their artwork references. Local metadata takes priority over remote providers, and an NFO-referenced image takes priority over provider art and images in media folders.
“Library scans became slow after enabling chapter previews.”
Chapter-image extraction requires video seeking, frame decoding, and image writes. Disable or limit that feature if visual chapter previews are less important than scan speed and metadata capacity; chapter markers can remain available without chapter images.
“Playback fails even though the source file is healthy.”
Check the transcode volume’s free space and whether it is RAM-backed or otherwise capacity-limited. Then review the client’s codec, resolution, bitrate, subtitle, and audio constraints. A failed transcode can be a storage-capacity problem rather than media corruption.
“The database is on a network share.”
Move the SQLite database to local storage as recommended by Jellyfin’s storage guidance, then verify permissions, service startup, and backup coverage before removing the old copy.
The practical takeaway for a new installation
Think of Jellyfin as an index and playback service layered over your filesystem, not as a program that silently clones every movie. Keep original media, persistent server data, regenerable metadata, and temporary transcodes in separate mental and operational categories. Confirm the actual configured paths, reserve free space for the largest likely transcode workload, keep the database local, and back up the database and the generated assets whose loss would be inconvenient to recreate.
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