{ title: "Compatibility", crumbs: [ { 'Reference Guide': '../ref/' }, ], }

# Compatibility

GoAhead supports the following standards:

- HTTP/1.1
- CGI 1.1
- Form-based File Upload in HTML

## API Compatibility

The GoAhead APIs are evolving, and are thus subject to change between minor releases. The documentation provides a Stability Classification for each API group that reflects their stability with regard to backwards compatibility.

We do not provide a blanket commitment to backward compatibility. Rather, we adopt a more surgical approach on an API by API basis.

## Migrating to GoAhead 3/4

GoAhead 3 is major upgrade relative to GoAhead 2. Some APIs have changed and new APIs have been added for increased functionality. Where the APIs have changed, their core functionality and operation typically remains similar. You can migrate code from GoAhead 2 to GoAhead 3 with simple refactoring.

GoAhead 4 is highly compatible with GoAhead 3. A small number of deprecated APIs were removed and the contract of some APIS have been strengthened by adding "const". However, GoAhead 3 applications should run unmodified in GoAhead 4.

### Legacy API Support

The configure command has an option to maximize backward compatibility and assist migration by supporting the legacy APIs. Use configure --set legacy=true to enable the legacy APIs.