REST vs gRPC: how should your services communicate?

When systems grow and split into separate services, the question of how they should communicate with each other inevitably arises. Two options stand out: REST, the universal standard built on HTTP, and gRPC, a modern high-performance protocol created by Google. They don't compete on exactly the same ground: REST shines in public APIs and browser communication, while gRPC excels at internal communication between services. Understanding when to use each one helps you avoid decisions that penalize performance or compatibility.

In this article we compare REST and gRPC, their strengths and their limits, and explain when each one is the better fit.

What REST is

REST is an API style based on HTTP in which you operate on resources using the standard methods, typically exchanging data in JSON format. Its great advantage is universality and simplicity: any client understands it, including the browser, it is human-readable, easy to debug, and backed by an enormous ecosystem. It is the default choice for public APIs, third-party integrations, and any communication where compatibility and ease of use matter more than extreme performance.

What gRPC is

gRPC is a high-performance communication protocol that uses HTTP/2 and exchanges data in a compact binary format (Protocol Buffers) instead of text. Its advantage is speed and efficiency: binary messages are far lighter and faster than JSON, it supports bidirectional streaming, and it automatically generates client and server code from a contract. It shines in internal communication between microservices, where performance and low latency are critical and both ends are under your control.

The key differences

These are the factors where the difference between REST and gRPC is most noticeable:

• Format: text (JSON) in REST; binary (Protocol Buffers) in gRPC.
• Performance: higher in gRPC; sufficient in REST.
• Compatibility: REST works everywhere; gRPC has limits in the browser.
• Readability: REST is readable; gRPC is not, since it is binary.
• Streaming: native and powerful in gRPC; limited in REST.
• Contract: strict and auto-generated in gRPC; more flexible in REST.

The browser factor

A decisive difference is browser compatibility. REST works natively from any web application, which makes it essential for the APIs a frontend consumes. gRPC, by contrast, does not work directly from the browser without an intermediate layer, so its natural territory is server-to-server communication. This limitation, more than a flaw, defines where each one fits: REST facing the outside world, gRPC inside the system.

Contract and maintenance

Another practical difference lies in how the communication is defined and maintained. gRPC starts from an explicit contract (the Protocol Buffers file) from which client and server code is generated automatically, which reduces errors and keeps both ends in sync: if the contract changes, both sides update consistently. REST, being more flexible, offers greater freedom but leaves it up to the team to maintain the discipline of documenting and versioning the API well so clients don't break. For internal systems that evolve quickly and where you control both sides, the strict contract of gRPC is a maintenance advantage; for public APIs with many external consumers, the flexibility and tolerance of REST usually weigh more.

When to choose each one

Choose REST for public APIs, third-party integrations, and any communication that must be consumed by a browser or a client you don't control: it wins on compatibility and simplicity. Choose gRPC for high-performance internal communication between microservices, where you control both ends and speed and efficiency are critical. Many systems use both: REST at the client-facing edge and gRPC between internal services. The key is to use each one in its natural territory.

At AxiomTech we design the communication between your systems with the right protocol, REST or gRPC, based on performance and compatibility. If you are defining the architecture of your services and aren't sure how to connect them, let's talk and we'll advise you based on your specific case.