Embedthis Appweb 4.3.4
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# Quick Nav

- API Compatibility
- Appweb 4
- Appweb 2

# See Also

# Compatibility

Appweb supports the following standards:

- HTTP/1.1
- CGI 1.1
- Form-based File Upload in HTML
- ECMA-262 for server side JavaScript if using Ejscript

## API Compatibility

The Appweb 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 Appweb 4

Appweb 4 is an evolutionary release relative to Appweb 3. Some APIs have changed and new APIs have been added for increased functionality. Appweb 4 uses a new memory allocator that does not require a memory context as the first argument to most APIs. So many APIs have changed signature, while the underlying functionality remains largely similar. The memory allocator uses garbage collection and this eliminates the need to manually free up memory. You can migrate code from Appweb 3 to Appweb 4 with refactoring.

If you are migrating from Appweb 2, you should regard Appweb 4.X as a next generation web server. You can migrate code from Appweb 2 to Appweb 4, however, you should anticipate significant refactoring work throughout the transition.

## Appweb 2

Appweb 2 is now officially deprecated.

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