Does Graph API support HTTP/2 ?

Question

Does Graph API support HTTP/2 ?

Yu, Miseon 5

Hi,

Based on the answer for https://learn.microsoft.com/en-us/answers/questions/5897760/does-graph-api-support-http-2-0 and the article https://m365admin.handsontek.net/microsoft-graph-to-support-http2-as-of-september-2023/ , I thought Graph API supports HTTP/2.

However, based on our experiment that was executed via cURL doesn't seems like that.

http2-prior-knowledge.log

Is this a bug or isn't HTTP/2 supported?

Best regards,

Miseon

Dennis Ameling 0

They say it's supported but the reality is different. The Graph API always uses HTTP/1.1 even if the client supports HTTP/2:

curl -sS -o /dev/null --http2 -v https://graph.microsoft.com/v1/me/messages 2>&1 | grep -i alpn
* ALPN: curl offers h2,http/1.1
* ALPN: server did not agree on a protocol. Uses default.

Whereas e.g. Outlook does support it:

curl -sS -o /dev/null --http2 -v https://outlook.cloud.microsoft 2>&1 | grep -i alpn
* ALPN: curl offers h2,http/1.1
* ALPN: server accepted h2

Your answer

Dennis Ameling 0 Reputation points

2026-09-11T12:26:07.4333333+00:00

They say it's supported but the reality is different. The Graph API always uses HTTP/1.1 even if the client supports HTTP/2:

curl -sS -o /dev/null --http2 -v https://graph.microsoft.com/v1/me/messages 2>&1 | grep -i alpn * ALPN: curl offers h2,http/1.1 * ALPN: server did not agree on a protocol. Uses default.

Whereas e.g. Outlook does support it:

curl -sS -o /dev/null --http2 -v https://outlook.cloud.microsoft 2>&1 | grep -i alpn * ALPN: curl offers h2,http/1.1 * ALPN: server accepted h2