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StringLane
iOS .strings · .xcstrings · Flutter ARB · Android XML · i18next JSON

One place for every locale
No more file-by-file

Stop adding the same key to five files by hand. StringLane shows every locale side-by-side, flags missing keys and broken placeholders before your users find them, and saves straight to your source files: no cloud, no export step

IDE for localization files · Local-first · Works offline

Download free trialSee how it works

No email · No credit card · Full app for 14 days

Sound familiar?

You already have a system. Here is why it keeps failing you.

Add one string. Now edit it five times.

A new key means opening every locale file and pasting the same key name into each one by hand, hoping you didn't skip Localizable.strings for German or fat-finger the key in ja.arb. The work grows with every language you support.

Comparing locales by hand is archaeology.

Open the German file, memorize a key, switch to French, search for it, switch to Japanese, lose your place, start over. At four locales you're not editing anymore. You're cross-referencing files in your head.

Your build passed. The translation didn't.

The key exists in every file, but the value is still in English. gen_l10n compiles clean, the tests pass, and a German user gets English UI. You find out from a 1-star review, not your toolchain.

You went wide with AI. Can you trust what shipped?

Paste 40 locales into a chatbot and it gives up mid-file on context limits. Xcode's built-in auto-translate can burn $40 in tokens for a single language. Neither gives you a surface to check what actually came back wrong.

See every locale at once. Trust what you ship.

Sync, verify, and fill every language from a single view

Know every gap before you submit

Missing keys, broken placeholders, ICU syntax errors, plural forms the target locale still needs: flagged the moment they exist, as one list across every locale. You see what's wrong before you touch the build command, not after a 1-star review.

Edit, save, commit, nothing else

StringLane writes directly to your ARB, .strings, XML, or JSON files on every keystroke. Your git workflow stays exactly as it is. There is no export step, no sync button, no intermediate format to manage.

Add a key once: every locale, one view

StringLane opens your folder, groups keys by namespace in the sidebar, and renders every locale for the active key side-by-side. Create a key and it lands in all of them at once, ready to fill: no pasting the same key name into five files, no toggling between editor tabs.

AI fill when you want it. Your key, checked before it lands

Bring your own key (OpenAI, Anthropic, Gemini, or fully local via Ollama) and sweep every missing string in one pass. Results land in the same validation view, checked before they ship. No per-character credits, no context limits, no copy-paste loops.

How it works

From open folder to ship-ready in minutes

Architecture note: StringLane runs entirely on your machine: no account, no cloud, no server your files pass through. Your locale files stay in your repo, in your exact format. A git diff before and after shows only the lines you changed.

Features

The localization IDE: built for locale files, not bolted onto a generic editor

Pricing

One price. No subscription. Yours forever.

Free Trial

$0/ 14 days

Full app, all features. No email, no account, works offline.

  • All five formats: ARB, .strings, .xcstrings, XML, JSON
  • Side-by-side locale editor
  • Real-time ICU & placeholder validation
  • AI translation: BYOK, no per-character fees
  • Auto-save directly to source files
  • 14 days · no credit card · works offline
Start free 14-day trial
Early-adopter price

Full License

$49one-time

Full price after launch: $79

One-time purchase. No annual renewal. No seat fee.

  • Everything in Free Trial
  • Lifetime license: pay once, use forever
  • 3 machine activations
  • All future updates within major version
  • Priority email support
  • Secured at early-adopter price ($79 after launch)
Buy Full License: $49

Instant download after purchase

Lokalise lists $144 a month at entry and $999 on Advanced (checked July 2026). StringLane covers all five formats, with validation, for $49 once.

Need more than 3 activations? Contact us and we'll sort it out.

FAQ

Frequently asked questions

Do I have to add each new key to every locale file by hand?
No. That's the whole point. Add a key once and StringLane writes it into every locale file at the same time, ready to fill. Rename or delete a key and the change propagates across all locales too: no pasting the same key name into five files, no find-and-replace, no key that lives in en.arb but goes silently missing from de.arb or ja.arb. Type the source string, then sweep the rest with AI or fill them in side-by-side: every locale stays in sync.
Will StringLane modify or reformat my localization files?
No, not in any of the five formats. StringLane reads your files, writes your edits back, and leaves everything else alone: ARB @key descriptions and key order, iOS .strings quoting style and comments, .xcstrings JSON shape, Android XML formatting and <plurals> ordering, i18next nested-vs-flat layout and CLDR suffix convention. It saves in the same format it found. Open the same file in VS Code before and after: the diff shows only the lines you actually changed.
What happens to my files if I uninstall StringLane?
Nothing. They stay exactly where they are, valid and unmodified. StringLane writes directly to your source files the whole time, so there is no export step and no proprietary format to escape. Your Flutter project, Xcode project, or Android project has no idea StringLane ever existed. It works fine without it.
Is ARB the main format and everything else an afterthought?
All five formats are first-class: ARB (Flutter), .strings (iOS), .xcstrings (Xcode 15+ String Catalog), Android XML, and i18next JSON. The core parser for each was built and tested independently, not shimmed on top of a JSON converter. You can open a mixed project and see missing keys flagged the same way across all of them. Plurals work per-format in their native shape: ICU for ARB and i18next, Apple variations for xcstrings, .stringsdict for iOS, and <plurals> for Android. If you're new to either: what the .xcstrings format is and what an ARB file is.
Does StringLane conflict with FlutterIntl or gen_l10n?
No. StringLane is a file editor, not a code generator and not a build tool. It edits the .arb files that FlutterIntl and gen_l10n already consume. Your l10n.yaml, your flutter gen-l10n command, your VS Code FlutterIntl extension. All of that keeps running exactly as before. StringLane sits one layer below all of it, at the file level.
Where do my strings go when I use AI translation?
Directly to whichever of the eight providers you configure: OpenAI, Anthropic, Google Gemini, Groq, Mistral, DeepSeek, xAI, or the Local LLM provider (any OpenAI-compatible runner: Ollama, LM Studio, Jan, llama.cpp, vLLM). The cloud providers use your own API key. StringLane has no server. Your strings never pass through StringLane infrastructure because there is no StringLane infrastructure. Pick the Local LLM provider and your data never leaves your machine. All eight providers use structured-output enforcement (JSON Schema, tool calls, or response schema) so bulk translations parse reliably end-to-end. Setting up AI translation takes about five minutes.
Can I run AI translation fully offline, with no cloud?
Yes. Pick Local LLM (OpenAI-compatible) in Settings → AI, then point StringLane at a runner you already have (Ollama, LM Studio, Jan, or anything that exposes an OpenAI-compatible HTTP API). Default base URL is http://localhost:11434/v1 for Ollama; type any model name your runner has pulled. No API key needed, no network required after the model is loaded. Full local-LLM walkthrough.
I already translate with ChatGPT or Claude. Why would I need this?
Keep doing that. StringLane is the layer that workflow is missing. It opens every locale file in your project at once, so there's no context window to overflow and no truncated output at 40 languages. Gaps, broken placeholders, and ICU errors are flagged live, and bulk-fill runs on your own key from the same provider (a one-time setup): no per-language copy-paste loop, no re-sending whole files through a chat window. Every change is written straight into your files, so your git diff shows exactly what the AI changed.
Is this another monthly subscription?
No, this is a one-time purchase. You pay once and you own it: no annual renewal, no seat fee, no “basic tier” that locks the features you actually need behind a higher plan. For comparison, Lokalise lists $144 a month at entry and $999 on its Advanced plan (checked July 2026). That bill arrives every month. Future updates within the major version are included. The current price is $49 (early-adopter). Full price after launch is $79.
I'm solo and this app might never make real money. Is this worth it?
If you have shipped or are close to shipping a localized app, yes. Adding a language goes from a weekend of file-juggling to an afternoon: add your keys once, fill every locale in one sweep, and even a single prevented release-blocking gen_l10n failure or user-facing translation gap pays for it. If localizing still feels optional right now, wait until you have four locales and a deadline. That is when this tool earns back its cost in a single afternoon.
Are there any limits on projects or keys?
No. Open as many projects as you want, with as many keys and locales as your files contain. StringLane reads directly from your file system. There's no database, no sync limit, no usage cap.
How do I find every missing translation across the project?
The Issues Panel (⌘J) lists every validation problem across the project as one row per (locale, key), missing translations, placeholder mismatches, ICU syntax errors, length warnings, guarded-word drift. Click a row to jump to that key, hit ✨ Auto-translate per row, or sweep the whole project with Fix all with AI. The Command Palette (⌘P) also exposes "Translate all missing with AI" for one-shot fills across every locale. How to use the Issues Panel.
How does it handle plurals in languages like Ukrainian or Polish?
When you translate a plural key into a locale that requires more forms than the source has (e.g. Ukrainian needs one, few, many, other), StringLane reads CLDR rules and auto-fills every quantity the target language needs in one click. You don't manually add + few / + many first. The visual ICU editor and per-locale plural panel handle the editing; validation badges call out quantities the target locale requires but you haven't filled. Working with ICU plurals covers the rules per format.
Does StringLane run on Windows and Linux, or just macOS?
All three, today: macOS (Apple Silicon and Intel, signed and notarised by Apple), Windows x64, and Linux (a self-updating AppImage, or a .deb if you prefer your package manager). One honest caveat: the Windows build isn't code-signed yet, so SmartScreen shows an “unknown publisher” warning on first run: click “More info” → “Run anyway”. Checksums for every build are published alongside the downloads.
New to the formats?What is .xcstrings?What is an ARB file?What is ICU MessageFormat?

Still have questions? Email us at support@stringlane.app

Stop juggling locale files by hand

StringLane adds a key to every locale at once, shows them side-by-side, and flags what's missing or broken before you ship. Edits saved straight to your source files, no cloud, no export step. One purchase, no subscription, yours to keep.

Start free 14-day trial

Early-adopter price: $49 one-time. Full price is $79.