gocryptfs uses ext4-style *feature flags* to add new functionality or better security to the on-disk-format. These are stored in `gocryptfs.conf` as `FeatureFlags`. When a new feature flag is added, gocryptfs will continue to support mounting older filesystems that do not have this flag set.

However, from time to time major gocryptfs revisions will drop support for very old filesystems. This keeps the gocryptfs code base clean and maintainable.

As seen on the table below, v1.0 will be the first version to drop support for very old filesystems (v0.6 and lower).

|                   | can be mounted on ▶                  | v0.4 | v0.5 | v0.6 | v0.7 | v0.8 | v0.9 | v0.10 | v1.0 |
|-------------------|--------------------------------------|------|------|------|------|------|------|-------|------|
| ▼ **created by**  | ▼ **feature flags**                  |      |      |      |      |      |      |       |      |
| v0.4              | -                                    | Y    | Y    | Y    | Y    | Y    | Y    | Y     | -    |
| v0.5              | DirIV                                | -    | Y    | Y    | Y    | Y    | Y    | Y     | -    |
| v0.6              | DirIV, EMENames                      | -    | -    | Y    | Y    | Y    | Y    | Y     | -    |
| v0.7, v0.8        | DirIV, EMENames, GCMIV128            | -    | -    | -    | Y    | Y    | Y    | Y     | Y    |
| v0.9, v0.10, v1.0 | DirIV, EMENames, GCMIV128, LongNames | -    | -    | -    | -    | -    | Y    | Y     | Y    |