What Is the .xcstrings Format? Xcode String Catalogs

.xcstrings is the file extension for String Catalogs, the localization format Apple introduced at WWDC 2023 to replace the older .strings and .stringsdict files. A String Catalog is a single JSON file that holds every locale for a target, plus a translation state for each string, so Xcode can show you, per language, what is new, what needs review, and what is done.

What it replaces#

The classic Apple approach split localization across formats:

• Localizable.strings: one file per locale, simple "key" = "value"; pairs.
• Localizable.stringsdict: a separate XML plist just for plurals.

String Catalogs fold all of that into one .xcstrings file per string table, with plural and device variations expressed inline. Xcode extracts strings into it automatically at build time.

What a String Catalog contains#

The file is JSON keyed by source string. Each entry stores its localizations and, critically, a state for every language:

• new: extracted but not yet translated.
• needs_review: translation exists but is flagged for a second look.
• translated: done.

It also tracks strings marked shouldTranslate: false, system-managed text that should be left alone, and a extractionState that records whether a string is still present in code.

Why the state model matters#

The per-string state is the feature, and it is also the thing hand-editing the JSON gets wrong. Edit a value in a text editor and the surrounding state does not update, so Xcode's "what still needs translating" view drifts out of sync with reality. Multiply that across a few hundred strings and several locales and the catalog becomes untrustworthy.

How StringLane works with .xcstrings#

StringLane reads and writes .xcstrings natively. It auto-detects the format by extension, loads every locale from the single file, and shows them side-by-side like any other project. A string Xcode has extracted but nobody has translated carries a grey New badge. When you edit and save, StringLane updates the state automatically (a non-empty value becomes translated, an empty one reverts to new) and locks shouldTranslate: false strings against editing. Adding a locale merges into the existing file rather than creating a new one, so the catalog stays canonical.

Two caveats on needs_review specifically, since it is the state that carries the most information. Catalogs spell it with an underscore and StringLane's badge matches a hyphenated spelling, so a string awaiting review currently shows no badge — in the screenshot above, French is needs_review and looks the same as a finished translation. Saving also recomputes every string's state from whether it has a value, which relabels needs_review as translated across the whole catalog. Until both are fixed, treat Xcode as the authority on review state.

Next steps#

• xcstrings editor: what StringLane validates in a String Catalog, and how translation state is kept in sync.
• How to Use the Format Editor: format-specific editing for iOS, Android, and i18next projects.
• How to Open a Localization Project: auto-detection and what StringLane loads.
• How to Add a New Locale: add a language column from a preset.