Free tool

Convert .arb to JSON

Flutter's Application Resource Bundle on one side, plain i18n JSON on the other, for when the same product ships as an app and a website.

Runs in your browser. No account, no upload, nothing leaves your machine.

.arbJSON

Runs in your browser. The file is never uploaded.

ARB is JSON with one rule

An .arb file is JSON where any key starting with @ is metadata about the key of the same name without it, and @@locale is metadata about the file. That single rule is why a straight JSON.parse gives you a file with twice as many keys as it should have, half of them objects. This tool separates the two: the strings become the JSON, and @key.description becomes the translator comment where the target format has room for one.

What survives

Converting is easy. Not breaking the file is the hard part.

Every converter that treats a language file as plain text will eventually ship you a crash. These are the three places it happens.

Placeholders stay placeholders
%@, %lld, %1$s, {name} and {{count}} come out exactly as they went in. A placeholder that got escaped, renumbered or translated is a crash on the device, not a typo.
Plural forms stay separate
Xcode variations, the Android plurals element and gettext msgstr[n] all mean the same thing and all spell it differently. They map onto each other here instead of collapsing into one string. Polish has four forms; all four survive.
Keys keep their shape
Nesting, dotted paths, arrays and translator comments carry across wherever the target format has somewhere to put them. Where it does not, the section below says so.

What does not come across

Written down here, because the alternative is finding out in a broken build.

Placeholder declarations do not survive. A block declaring that count is an int formatted as compact carries type information the intermediate form has no field for, and a guessed type is worse than a missing one: flutter gen-l10n would generate a wrongly typed method signature from it. ICU plural syntax inside the value itself, {count, plural, one {…} other {…}}, is passed through untouched, because for ARB that is ordinary text.

How it works

  1. Step 1

    Drop the file in

    Drag your .arb onto the left box, pick it with the file button, or paste the text. Nothing is uploaded. The conversion runs in this tab.

  2. Step 2

    Read the result

    The JSON appears as you type. The counter under the box says how many keys came through, so a file that lost half its content is visible immediately.

  3. Step 3

    Copy or download

    Take the text to the clipboard, or download it with the right extension. Swap the arrow to go the other way.

One language file in. 64 languages out.

Converting a format is the part you can do by hand. Translating 3,627 keys into 64 languages without breaking a single placeholder is the part you cannot. On the next release you only pay for the strings that changed.

Create account

€19 per month incl. VAT, cancellable monthly.

Questions

Do ICU plurals inside the string survive?
Yes, verbatim. In ARB, plurals live inside the value as ICU syntax, {count, plural, one {…} other {…}}, rather than in a separate structure, so the converter treats them as text and does not touch a brace.
What about @@locale?
It is read as file metadata and not turned into a translatable key. Converting back, an @@locale is written for the language you are targeting.
Can I go JSON to .arb for a new Flutter app?
Yes, swap the direction. You get valid ARB with @@locale and a description block for every key that carried a comment. You will still want to add placeholders declarations by hand for any string with typed arguments.
Does it handle a .arb with 3,000 keys?
Yes. Everything runs locally, so the only limit is your browser's memory, not an upload size or a rate limit.

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