# refraction-networking/utls

Fork of the Go standard TLS library, providing low-level access to the ClientHello for mimicry purposes.

Repository: https://github.com/refraction-networking/utls
Canonical: https://ross.abutalabs.com/products/utls
Language: Go
License: BSD-3-Clause
License Family: permissive
Topics: tls, clienthello, parrot, low-level-tls, golang, crypto, handshake, tls-extension, cipher-suites, obfuscation, anticensorship
Last push: 2026-08-02T15:17:17+00:00

## Health v2 (maintenance only)
Score: 81/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 95, release rhythm 53, longevity 100
- inputs: {"age_days": 3284, "days_push": 31, "days_rel": 232, "gap_med": 41.0, "n_releases_24m": 7}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2539, forks 362 (observed 2026-08-28T04:06:59.278964+00:00)

## What it is
uTLS is a fork of Go's crypto/tls library that provides low-level access to the TLS ClientHello message, enabling fingerprint mimicry and resistance to ClientHello-based blocking. It is widely used by anti-censorship tools to make Go's distinctive TLS handshake look like common browsers or other clients.

## Use cases
- make my Go program's TLS handshake look like Chrome to avoid blocking
- customize ClientHello extensions and cipher suites in Go
- build a censorship-resistant proxy that isn't fingerprinted by its TLS
- randomize TLS fingerprints to defeat blacklists
- mimic browser TLS fingerprints in a Go client
- access and modify low-level TLS handshake fields

## When to choose
- you need to disguise or randomize Go's TLS ClientHello fingerprint
- you're building anti-censorship or privacy tooling in Go
- you need low-level read/write access to TLS handshake messages

## When to avoid
- you just need standard TLS connections without fingerprint concerns
- you're not working in Go
- you need a high-level HTTP client rather than TLS-level control

## Facets
- artifact type: library
- maturity: active
- function: cryptography, security, http-client, networking
- domain: security, privacy, censorship-circumvention, networking, developer-tools
- platform: go, cross-platform
- tags: tls, clienthello, fingerprinting, anti-censorship, obfuscation, parrot, handshake, crypto-tls-fork

## Member repositories
- refraction-networking/utls (main) score 81

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:59.278964+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 2026-08-30T02:25:10.424191+00:00, confidence not recorded.
  - readme: https://github.com/refraction-networking/utls (fetched 2026-08-28T04:06:59.278964+00:00, sha 68be6b9c7bda)
- Data as of 2026-08-30T08:39:29.467469+00:00.