# cel-expr/cel-go

Fast, portable, non-Turing complete expression evaluation with gradual typing (Go)

Repository: https://github.com/cel-expr/cel-go
Canonical: https://ross.abutalabs.com/products/cel-go
Homepage: https://cel.dev
Language: Go
License: Apache-2.0
License Family: permissive
Topics: golang, go, cel, expression, expression-language, expression-evaluator, expression-parser
Last push: 2026-08-26T22:05:02+00:00

## Health v2 (maintenance only)
Score: 99/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 98, longevity 100
- inputs: {"age_days": 3099, "days_push": 7, "days_rel": 14, "gap_med": 21.0, "n_releases_24m": 19}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3085, forks 305 (observed 2026-08-28T04:07:42.072895+00:00)

## What it is
cel-go is a Go implementation of the Common Expression Language (CEL), a fast, portable, non-Turing complete expression language with gradual typing. It parses, type-checks, and evaluates single expressions against host-provided variables and functions, making it safe to embed in performance-critical applications.

## Use cases
- evaluate authorization rules for API requests
- add user-defined filter expressions to API list calls
- validate protocol buffer messages with declarative constraints
- embed a safe sandboxed expression evaluator in a Go application
- evaluate policy predicates over structured data like JWT claims
- let users write simple configuration expressions without scripting languages

## When to choose
- you need fast, predictable-cost expression evaluation in Go (nanoseconds to microseconds)
- you want a safe, non-Turing complete alternative to embedding a full scripting language
- you need type-checked expressions over protobufs, JSON, lists, and maps
- you're building policy, validation, or filtering features where expressions change rarely but evaluate often

## When to avoid
- you need a full scripting language with loops, state, or side effects
- your application is not written in Go or targeting the Go ecosystem
- you need Turing-complete programmability or user-defined functions with complex control flow

## Facets
- artifact type: library
- maturity: stable
- function: parser, interpreter, security, authorization
- domain: programming-languages, developer-tools, security, apis
- platform: go, cross-platform
- tags: expression-language, cel, policy-engine, type-checking, non-turing-complete, sandboxed-evaluation

## Member repositories
- cel-expr/cel-go (main) score 99

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:07:42.072895+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T07:27:39.270912+00:00, confidence not recorded.
  - readme: https://github.com/cel-expr/cel-go (fetched 2026-08-28T04:07:42.072895+00:00, sha edaaaea72520)
  - homepage: https://cel.dev (fetched 2026-08-29T09:42:46.523064+00:00, sha a1e22045bb63)
- Data as of 2026-08-30T08:39:29.467469+00:00.