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description=Configure API version schemes using info.version and x-fern-version;

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Text of the page (random words):
api version openapi fern documentation for ai agents a documentation index is available at the root level at llms txt append llms txt to any url for a page level index or md for the markdown version of any page search ask ai book a demo log in start for free overview what is an api definition project structure openapi overview overlays overrides authentication servers sync your specification endpoints extensions overview api version audiences availability base path default values enum descriptions names and availability request response examples api explorer control global headers ignoring elements sdk method names sdk variables tag display names parameter names property names idempotency pagination retry behavior schema names server names and url templating integrate your server framework generators yml reference asyncapi openrpc grpc fern definition what is an api definition project structure overview overlays overrides authentication servers sync your specification http json endpoints webhooks multipart form uploads server sent events overview api version audiences availability base path default values enum descriptions names and availability request response examples api explorer control global headers ignoring elements sdk method names sdk variables tag display names parameter names property names idempotency pagination retry behavior schema names server names and url templating fastapi generators yml reference overview overrides authentication servers sync your specification publish subscribe operations message formats message bindings overview audiences availability request response examples ignoring elements server names overview overrides authentication servers sync your specification json rpc methods overview audiences availability request response examples ignoring elements sdk method names sdk group names server names overview overrides authentication servers sync your specification grpc services streaming error handling generators yml reference overview authentication types overview http json endpoints multipart form uploads bytes server sent events webhooks websockets errors imports examples audiences availability overview environments global headers errors packages depending on other apis export to openapi book a demo log in start for free english light on this page info version x fern version scroll to top openapi extensions api version ask a question copy page view as markdown more actions fern supports two complementary ways to express the version of your api info version records a single version string that flows through to your generated docs and downloadable spec x fern version defines a header based version scheme for apis that dispatch behavior based on a version header similar to stripe s stripe version info version fern preserves the info version field from your openapi specification any format is supported including semver 1 2 3 calver 2026 06 23 or custom strings openapi yml 1 openapi 3 1 0 2 info 3 title my api 4 version 2026 06 23 5 paths the value carries through to the downloadable openapi spec served from your docs site and to markdown output on api reference pages x fern version to define a header based api version scheme use x fern version openapi yml 1 x fern version 2 header x api version 3 default 2 0 0 4 values 5 1 0 0 6 2 0 0 7 latest 8 paths this generates a version selector dropdown in the api reference and attaches the chosen version as a request header on each call was this page helpful yes no edit this page previous extensions overview next use audiences to filter your api checking status soc 2 soc 2 type ii 2026 fern birch solutions inc a postman company documentation sdks docs ask fern cli reference api definitions openapi asyncapi openrpc grpc resources blog support pricing company brand kit privacy policy terms of service api definitions api definitions import and configure your api specifications english api definitions api definitions import and configure your api specifications