Support gzip compression

[marandaneto]

Is your feature request related to a problem?

When using captureMode=form, the compression is lz64 (base64).
When using captureMode=json, there's no compression.

Describe the solution you'd like

When using captureMode=json, we could either use gzip by default if possible, or offer another config to allow or not allow the gzip compression.
JS SDK has an option disable_compression: boolean.

Describe alternatives you've considered

Related sub-libraries

• All of them
• posthog-web
• posthog-node
• posthog-react-native

Additional context

Thank you for your feature request – we love each and every one!

[raikasdev]

Hey! For the lite package could this perhaps utilize the Compression Streams API (which is still newly available but becomes mainline in November 2025), which would possibly allow not having to include the fflate dependency. On the backend side the API has been stable since Node v18 and Deno v1.19, with no support yet for Bun. If the API isn't available it could just fallback to no compression.

If that sounds good I could perhaps work on this and submit a PR 👍

[marandaneto]

Could be part of https://github.com/PostHog/posthog-js-lite/tree/v5 (#468)

For the lite package could this perhaps utilize the Compression Streams API (which is still newly available but becomes mainline in November 2025), which would possibly allow not having to include the fflate dependency

and fallback to no compression if not available.

On the backend side the API has been stable since Node v18 and Deno v1.19, with no support yet for Bun. If the API isn't available it could just fallback to no compression.

yep, that's great.

i'd love to see a PR.