docs(surveys): add survey translations guide

[lucasheriques]

Summary

Documents the survey translations feature now shipped across all four PostHog SDKs.

Covers:

• How the SDK resolves a display language at runtime (explicit override → language person property → device/browser locale).
• The case-insensitive matching algorithm with base-language fallback (e.g. pt-BR → pt).
• Which fields are translatable at the survey and question level, and which intentionally are not (the survey-level description).
• Per-SDK configuration snippets for the overrideDisplayLanguage / override_display_language option.
• The $survey_language event property and how to use it for breakdowns.
• A short FAQ.

SDK versions referenced

SDK	Minimum version
posthog-js	1.372.3
posthog-react-native	4.44.0
posthog-ios	3.59.0
posthog-android	3.45.0

iOS and Android merged today; their version numbers will be cut on the next releases of posthog-ios (`3.59.0`) and posthog-android (`3.45.0`) via their changeset/release workflows.

Screenshots needed (follow-up)

The doc contains two placeholder comments (``) for visuals that would make the page sharper but require access to the production app UI:

1. Survey editor → Translations panel — language picker + the per-language fields for `name`, `thankYouMessage*`, per-question `question` / `description` / `buttonText` / `choices` / `lowerBoundLabel` / `upperBoundLabel`. Light + dark mode.
2. Insight breakdown by `$survey_language` — `survey sent` event with `$survey_language` as the breakdown dimension.

Happy to follow up with the actual images once captured, or another contributor can swap them in.

Test plan

• Doc renders without MDX errors locally (`gatsby develop`).
• Sidebar shows "Translating surveys" between "Conditional questions" and the "PostHog AI" section header.
• All anchor links in the doc resolve.
• Code snippets compile against the documented SDK versions.

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Created with PostHog Code

[github-actions]

Deploy preview

Status	Details	Updated (UTC)
🟢 Ready	View preview	May 21, 2026 09:41PM

[github-actions]

Vale prose linter → found 4 errors, 10 warnings, 7 suggestions in your markdown

Full report → Copy the linter results into an LLM to batch-fix issues.

Linter being weird? Update the rules!

contents/docs/surveys/translations.mdx — 4 errors, 10 warnings, 7 suggestions

Line	Severity	Message	Rule
2:20	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
11:158	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
18:46	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
27:35	error	Hi, Andy here... use an en dash ( – ) with spaces. On Mac, holding down the Option and hyphen key will give you an en dash.	PostHogBase.EnDash
27:69	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
53:154	error	Hi, Andy here... use an en dash ( – ) with spaces. On Mac, holding down the Option and hyphen key will give you an en dash.	PostHogBase.EnDash
63:3	warning	Use 'PostHog' instead of 'posthog'.	Vale.Terms
64:3	warning	Use 'PostHog' instead of 'posthog'.	Vale.Terms
65:3	warning	Use 'PostHog' instead of 'posthog'.	Vale.Terms
65:11	warning	Use 'iOS' instead of 'ios'.	Vale.Terms
66:3	warning	Use 'PostHog' instead of 'posthog'.	Vale.Terms
66:11	warning	Use 'Android' instead of 'android'.	Vale.Terms
72:53	error	Hi, Andy here... use an en dash ( – ) with spaces. On Mac, holding down the Option and hyphen key will give you an en dash.	PostHogBase.EnDash
72:73	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
72:205	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
128:48	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
128:135	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
140:124	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
140:175	warning	Avoid trivializing words. 'easy to' can sound dismissive to the reader.	PostHogDocs.Trivializers
150:86	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
160:68	error	Hi, Andy here... use an en dash ( – ) with spaces. On Mac, holding down the Option and hyphen key will give you an en dash.	PostHogBase.EnDash