21 breaking releases

Uses new Rust 2021

new 0.21.0 Dec 3, 2021
0.20.0 Nov 24, 2021
0.19.0 Nov 17, 2021
0.8.0 Jul 2, 2021
0.1.0 Mar 26, 2021

#3 in #deno

Download history 3721/week @ 2021-08-15 3617/week @ 2021-08-22 3138/week @ 2021-08-29 3574/week @ 2021-09-05 5070/week @ 2021-09-12 3570/week @ 2021-09-19 3639/week @ 2021-09-26 4331/week @ 2021-10-03 4209/week @ 2021-10-10 3619/week @ 2021-10-17 2586/week @ 2021-10-24 1884/week @ 2021-10-31 2296/week @ 2021-11-07 2495/week @ 2021-11-14 1998/week @ 2021-11-21 1982/week @ 2021-11-28

8,897 downloads per month
Used in 29 crates (2 directly)

MIT license



Author: Aaron O'Mullan aaron.omullan@gmail.com

Serde support for encoding/decoding (rusty_)v8 values.

Broadly serde_v8 aims to provide an expressive but ~maximally efficient encoding layer to biject rust & v8/js values. It's a core component of deno's op-layer and is used to encode/decode all non-buffer values.

Original issue: denoland/deno#9540


serde_v8 fits naturally into the serde ecosystem, so if you've already used serde or serde_json, serde_v8's API should be very familiar.

serde_v8 exposes two key-functions:

  • to_v8: maps rust->v8, similar to serde_json::to_string, ...
  • from_v8: maps v8->rust, similar to serde_json::from_str, ...

Best practices

Whilst serde_v8 is compatible with serde_json::Value it's important to keep in mind that serde_json::Value is essentially a loosely-typed value (think nested HashMaps), so when writing ops we recommend directly using rust structs/tuples or primitives, since mapping to serde_json::Value will add extra overhead and result in slower ops.

I also recommend avoiding unecessary "wrappers", if your op takes a single-keyed struct, consider unwrapping that as a plain value unless you plan to add fields in the near-future.

Instead of returning "nothing" via Ok(json!({})), change your return type to rust's unit type () and returning Ok(()), serde_v8 will efficiently encode that as a JS null.

Advanced features

If you need to mix rust & v8 values in structs/tuples, you can use the special serde_v8::Value type, which will passthrough the original v8 value untouched when encoding/decoding.


  • Experiment with KeyCache to optimize struct keys
  • Experiment with external v8 strings
  • Explore using json-stringifier.cc's fast-paths for arrays
  • Improve tests to test parity with serde_json (should be mostly interchangeable)
  • Consider a Payload type that's deserializable by itself (holds scope & value)
  • Ensure we return errors instead of panicking on .unwrap()s


~1M SLoC