Protocols

OTLP gRPC vs HTTP: Which Should You Use

A practical comparison for choosing between the two OTLP transport options in a real deployment.

OpenTelemetry's wire protocol, OTLP, ships in two transport flavors: gRPC and HTTP (with either protobuf or JSON encoding). Most getting-started guides default to gRPC without much explanation, which leaves people who hit a firewall, proxy, or debugging wall wondering whether they picked wrong. Usually they didn't — they just hit one of the real, specific tradeoffs between the two.

The core difference that actually matters

gRPC uses HTTP/2 with a persistent, multiplexed binary connection. HTTP uses standard request/response semantics, either as binary protobuf or (less commonly) plain JSON. That one difference cascades into almost everything else below.

Factor	gRPC	HTTP
Default port	4317	4318
Connection model	Persistent, multiplexed	Per-request (or HTTP keep-alive)
Proxy/firewall friendliness	Can require HTTP/2-aware infrastructure	Works through almost any standard HTTP proxy
Payload inspection	Binary — hard to read raw	JSON variant is human-readable
Typical overhead	Lower, especially at high volume	Slightly higher per-request overhead

When gRPC is the right call

High-volume production traffic. The persistent multiplexed connection genuinely reduces overhead when you're sending thousands of spans per second — you're not paying connection setup cost per batch.
Your infrastructure already speaks gRPC. If your collector, service mesh, and internal tooling are already gRPC-native, staying consistent avoids adding a second protocol to reason about.
You control the network path end-to-end. Internal, same-cluster traffic where you're not fighting a corporate proxy or an old load balancer that only understands HTTP/1.1.

When HTTP is the right call

You're going through infrastructure you don't fully control. Corporate proxies, some API gateways, and older load balancers can mishandle or outright block HTTP/2-based gRPC traffic. Plain HTTP rarely has this problem.
You need to debug what's actually being sent. The JSON-encoded HTTP variant is directly readable in a packet capture or a simple curl test — gRPC's binary framing isn't something you can eyeball.
You're doing local development or testing. One less thing to get wrong when you're just trying to confirm a collector receives anything at all.

A specific, common failure mode: a gRPC exporter reports "connection established" while telemetry silently fails to arrive — this is often an HTTP/1.1-only proxy sitting in the path, silently mangling the HTTP/2 framing gRPC depends on. If exports look "connected but empty," HTTP is a fast way to rule out whether the transport itself is the problem before debugging anything else. See our guide on testing your collector configuration for the full check.

Testing both before committing

Since this is fundamentally an infrastructure compatibility question, not just a preference, it's worth testing both transports against your actual network path before locking one in — especially if any part of the route involves infrastructure you don't fully control. OTel Studio supports both protocols per endpoint, including sending to two endpoints on different transports simultaneously, so you can directly compare delivery reliability rather than guessing.

Neither is universally "better" — gRPC is more efficient when nothing's in the way, HTTP is more forgiving when something is. Test against your actual network path rather than defaulting to whichever the docs mentioned first.