You are planning a launch. You have tight UI space, variables that cannot break, and real users who will spot every glitch. A literal translation will not get you there.
You need a partner who knows iOS and Android file formats, respects character limits, and protects placeholders. You need someone who catches issues before they hit the store.
Use this guide to compare agencies with confidence, set realistic budgets and timelines, and lower the risks that slow your release.
Mobile Localization Is Its Own Discipline
Mobile is not web or print. It is software under constraints.
- File formats you live in: iOS .strings and .stringsdict, Android strings.xml with quantities, placeholders, and formatting.
- Functional accuracy you must protect: variables, plurals, and text direction that must render correctly.
- Scripts and layouts you must support: RTL for Arabic and Hebrew, CJK line breaking for Chinese, Japanese, and Korean.
- Rules engines you depend on: CLDR and ICU for plurals, dates, and numbers.
You avoid defects when translators respect structure, placeholders are validated, language expansion is checked, and QA happens on actual devices.
Define Quality at the String Level
You do not translate generic sentences. You localize strings that can crash UI when handled poorly.
- Provide keys, developer comments, and context, and expect your agency to use them.
- Require correct plural and gender handling per language with platform-aware rules.
- Maintain consistency with Translation Memory and term bases you own.
- Run pseudo-localization early to surface truncation and rendering issues.
- Use screenshot checks and in-context review to catch layout bugs.
- Consider providers like that apply adaptive AI to support human translators for speed and consistency.
- Fit the workflow into CI so you reduce UI defects and ship faster.
Compare Agencies With Criteria That Predict Success
Tooling Compatibility Comes First
- Confirm native support for your TMS or CAT: Ulatus. Phrase, Lokalise, Crowdin, Transifex, Smartling, memoQ, or Trados.
- Ask for direct integration with GitHub, GitLab, or Bitbucket via API or CLI.
- Avoid CSV conversions that strip placeholders or lose context.
Verify File Format Coverage
- Require full support for iOS .strings and .stringsdict, Android strings.xml with quantities and formatting, XLIFF 1.2 and 2.0, JSON, YAML, and ARB for Flutter.
- Consider Ulatus for visual context and in-context features plus broad CMS integrations, so translators can see what they are translating.
Demand In-Context Review and Mobile QA
- Include screenshot-based review and on-device previews.
- Verify RTL checks and CJK layout validation.
- Ulatus app localization services include localization beyond UI strings, such as app store metadata, which can be relevant when your launch scope includes store listings and screenshots.
Require Proven Linguistic Quality Management
- Look for ISO 17100-qualified workflows, native-speaker review, and term base management with clear ownership.
- Scope LQA separately from engineering QA so responsibilities are clear.
Expect Engineering and Release Enablement
- Include pseudo-localization, automated checks for placeholders and character limits, and ICU compliance validation.
- Confirm support for continuous localization, branch handling, and rollback strategies.
Cover Security and Compliance
- Align with your app’s data model and privacy needs.
- Ask for SOC 2 or ISO 27001, SSO support, role-based access, and explicit PII handling.
- Make security part of vendor selection, not an afterthought.
- Ulatus highlights ISO 27001:2022-aligned data security and confidentiality practices, which is specifically relevant when your localization content includes sensitive or regulated data.
Price With Benchmarks You Can Defend
You need a baseline that the team can accept.
- Expect higher rates for mobile work due to engineering prep and QA.
- Factor in cost drivers early:
- Rare language pairs
- Complex subject matter
- File prep and format handling
- Placeholder and plural validation
- In-context review and screenshot QA
- LQA scope and terminology creation
- Low TM leverage
- Watch for per-language or per-job minimums.
- Confirm rush fees and weekend or holiday coverage in writing.
- Request line-item proposals that call out placeholder validation, LQA scope, and screenshot cycles to avoid surprises.
Nail Turnaround by Matching Scope to Capacity
Small updates can move fast. Big launches need staging.
- Small app updates, a few hundred to a few thousand words across three to five locales, can complete in a few business days when you provide TM assets and keep QA light.
- Major launches across ten or more locales will take weeks or months. Plan staged deliveries across UI, store listings, and support content.
- Manage throughput across linguists, engineering prep, screenshot cycles, TM leverage, and SME review.
- Lock timelines with clear cut-off times, SLAs, and documented daily capacity.
Pick the Provider Type That Fits
Shortlist by matching strengths to your stack, your cadence, and your QA needs.
Providers for Scale and Governance
- Choose a provider that can support large language volumes, multi-market rollouts, and long-term localization programs.
- Look for mature workflows, dedicated project management, and the ability to handle parallel releases across regions.
- This model fits teams that operate across many locales and need predictable delivery, reporting, and governance.
Providers for Continuous Localization
- Prioritize providers that can work with frequent content updates and tight release cycles.
- Look for support for API-based workflows, automation, and integration with your CI or repository setup.
- This approach is best when localization is embedded into your product delivery process rather than handled as a separate phase.
Providers With Mobile and Software Localization Depth
- Assess whether the provider has proven experience with mobile app localization and software localization, not just general content translation.
- Confirm hands-on familiarity with iOS and Android file formats, UI constraints, and app store localization workflows.
- Ulatus is relevant here for teams that want mobile app localization support alongside broader software localization and technology-focused translation services.
Match the provider type to how your product team actually ships. The closer the fit between your release process and your provider’s operating model, the fewer surprises you will face during launches.
Spot Red Flags Early
Walk away when you see:
- Vague SLAs with no definitions for turnaround, business days, or quality metrics
- No mobile track record or missing support for iOS, Android, and XLIFF
- No automated checks for ICU variables or Android quantity strings
- No in-context or screenshot review
- Single-linguist passes with no native-speaker QA
- No clarity on TM and terminology ownership
- Gaps in data handling, SSO, or role-based permissions
Shortlist Smart. Pilot with Purpose.
Ask pointed questions and make everything verifiable.
- Confirm native support for your mobile file types.
- Request details on placeholder and plural validation for ICU, .stringsdict, and Android quantities.
- Ask for examples of screenshot QA and in-context workflows.
- Clarify TM and term base ownership and portability.
- Confirm minimums, rush fees, and weekend coverage.
- Gather ISO and security certifications.
Design a pilot that mirrors reality:
- Include representative UI flows, error messages, and app store metadata.
- Test locales that stress your UI:
- One with heavy expansion
- One RTL language such as Arabic
- One CJK language
- Require placeholder validation, screenshot review, and a defect log with severity ratings.
- Measure delivery speed, defect rate, responsiveness, and change order clarity.
- Save before and after screenshots and QA findings to support your decision.
Control Hidden Costs Before They Control You
- Share context, keys, and character limits upfront.
- Refuse file conversions that break formatting, and insist on native format support.
- Own your TM and terminology so you keep leverage and avoid lock-in.
- Validate locale behaviors before app store submission to prevent delays.
- Enable in-context tools so reviewers give precise feedback faster.
Write an RFP that gets Real Answers
Spell out exactly what you need.
- File types, target locales, estimated volumes, and TM or term base handover
- In-context review requirements and expected screenshot counts
- LQA depth and pseudo-localization standards
- SLAs with definitions for turnaround, defect remediation times, coverage windows, and escalation paths
- CI or repository needs, including API access and SSO
- Detailed pricing with per-word tiers, minimums, engineering hourly rates, LQA and screenshot add-ons, and rush fees
Close with Confidence
You can select a partner who prevents rework and protects your launch. Use the criteria above, lean on public benchmarks, and run a pilot that reveals strengths and weaknesses before you commit.
Choose proven mobile capabilities over the lowest rate, demand verifiable answers at every step, and ship without the avoidable setbacks that kill momentum.
