FlatBuffers
Hacker ApprovedRanked 5 of 9 serialization formats by recommenders
Fast binary serialization format that reads data without parsing, often recommended over Protocol Buffers; critics say its output can be large and bloated.
Fast binary serialization format that reads data without parsing, often recommended over Protocol Buffers; critics say its output can be large and bloated.
20 people gave an opinion
- recommend it
- 16
- criticize it
- 4
- approval share
- 80%
Recommended in 5 of 13 months
- November 2025: not recommended
- December 2025: recommended
- January 2026: recommended
- February 2026: not recommended
- March 2026: recommended
- April 2026: recommended
- May 2026: not recommended
- June 2026: not recommended
- July 2026: not recommended
- August 2026: recommended
- September 2026: not recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it carries the badge
- 16 people recommend itNeeds 10 or more, met.
- 4 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 5 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Fast zero-copy random access
“easy to work with, great size (esp compressed), random access, close-to-optimal parsing, extensible”
Comment from 23 Jan 2026 in “Replacing Protobuf with Rust to go 5 times faster” “can be much faster. Like, faster by an arbitrarily large factor, for data at rest.”
Comment from 2 Dec 2025 in “Why I stopped using JSON for my APIs” “I think it is used in many places that needs zero-copy”
Comment from 23 Jan 2026 in “Replacing Protobuf with Rust to go 5 times faster” - Comment from 20 Apr 2026 in “Zero-copy protobuf and ConnectRPC for Rust”
Better than Protobuf
“ASN.1, Cap'n Proto and Flatbuffers are all more efficient and exist already.”
Comment from 23 Jan 2026 in “Replacing Protobuf with Rust to go 5 times faster” “they might as well go to flatbuffers, which is much better than PB”
Comment from 2 Dec 2025 in “Why I stopped using JSON for my APIs” “switch to flatbuffers before you realize it's better than PB”
Comment from 2 Dec 2025 in “Why I stopped using JSON for my APIs” Large speed gains in projects
“FlatBuffers was definitely the majority of the improvements here!”
Comment from 6 Jan 2026 in “Brave overhauled its Rust adblock engine with FlatBuffers, cutting memory 75%” “outperforms Google Flatbuffers by 242x”
Comment from 23 Jan 2026 in “Replacing Protobuf with Rust to go 5 times faster” Extensible, useful beyond speed
“easy to work with, great size (esp compressed), random access, close-to-optimal parsing, extensible”
Comment from 23 Jan 2026 in “Replacing Protobuf with Rust to go 5 times faster” “That's something flatbuffers/capnproto do well that isn't just pure speed.”
Comment from 19 Dec 2025 in “Lite^3, a JSON-compatible zero-copy serialization format”
What people warn about
Each mark is one comment
Large, bloated output and code
“Cap’n Proto and FlatBuffers are fast but often produce rather large output”
Comment from 2 Mar 2026 in “Why does C have the best file API” “Flatbuffers etc. is cool but they can be very bloaty and clunky.”
Comment from 3 Mar 2026 in “Why does C have the best file API” “Flat buffers is know to bloat client code.”
Comment from 6 Jan 2026 in “Brave overhauled its Rust adblock engine with FlatBuffers, cutting memory 75%”
Other serialization formats people recommend
The four most recommended other serialization formats, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| Protocol Buffers (protobuf) | 77 | 66 | 54% | 10 | 10 yrs3 owners | — |
| Serde | 22 | 16 | 58% | 10 | — | — |
| Cap'n Proto | 20 | 5 | 80% | 7 | — | Approved |
| Protobuf | 19 | 25 | 43% | 8 | — | — |
| FlatBuffersThis page | 16 | 4 | 80% | 5 | — | Approved |
What people said
All 21 comments that mention it, newest first. Each links to the original comment.
“designing a more compact format doesn’t really buy much on modern CPUs and modern networks”
“that's a neat idea in general”
“it was buggy, opened half a dozen PRs to flatbuffers repo which got ignored”
“you need something like FlatBuffers for that”
“It's cool, but I personally think that for most use cases (not all)”
“Flatbuffers etc. is cool but they can be very bloaty and clunky.”
“Cap’n Proto and FlatBuffers are fast but often produce rather large output”
“ASN.1, Cap'n Proto and Flatbuffers are all more efficient and exist already.”
“outperforms Google Flatbuffers by 242x”
“I think it is used in many places that needs zero-copy”
“easy to work with, great size (esp compressed), random access, close-to-optimal parsing, extensible”
“There were a few features that core flatbuffers didn't have that I needed”
“it's the same idea in CapnProto or Flatbuffers”
“Don't run flatc on a JSON, it doesn't do that.”
“Flat buffers is know to bloat client code.”
“FlatBuffers was definitely the majority of the improvements here!”
“we explored things like FlatBuffers and their variants, but nothing came close to our system in terms of ease of use, versioning support, and performance”
“That's something flatbuffers/capnproto do well that isn't just pure speed.”
“can be much faster. Like, faster by an arbitrarily large factor, for data at rest.”
“they might as well go to flatbuffers, which is much better than PB”
“switch to flatbuffers before you realize it's better than PB”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.