# FIDL binary-compatibility (ABI) and source-compatibility (API) guide

This guide predated both FIDL versioning (API levels using `@available`) and
unknown interactions (`open` protocols and `flexible` methods). It gave poor
guidance that didn't reflect current policy or best practice. We hope to
eventually provide new, accurate instructions for platform interface evolution.
[](https://issues.fuchsia.dev/issues/new?component=1439230&template=1881640&description=Issue+on:+https://fuchsia.dev/docs/development/languages/fidl/guides/compatibility/README.md "Report a bug or suggest improvements on this page") [](https://cs.opensource.google/fuchsia/fuchsia/+/main:docs/development/languages/fidl/guides/compatibility/README.md "View the source code of this page") [](https://ci.android.com/edit?repo=fuchsia/fuchsia/main&file=docs/development/languages/fidl/guides/compatibility/README.md&cloneRepo=fuchsia/fuchsia:refs/heads/main&fullPath=fuchsia/docs/development/languages/fidl/guides/compatibility/README.md "Edit the source code of this page")