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What are client profiles?

Client profiles are pre-configured settings that replicate the exact TLS and HTTP fingerprints of real browsers. Each profile contains:
  • TLS fingerprint - ClientHello parameters, cipher suites, extensions
  • HTTP/2 settings - SETTINGS frames, priorities, flow control
  • HTTP/3 settings - QUIC parameters, frame types, pseudo-header order
  • Protocol behavior - Connection flow, stream IDs, GREASE values
Profiles are extracted from real browser traffic captures and updated regularly to match the latest browser versions.

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Available browser profiles

The library includes profiles for major browsers across versions:

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Chrome profiles

import "github.com/bogdanfinn/tls-client/profiles"

// Latest versions
profiles.Chrome_146
profiles.Chrome_146_PSK  // With session resumption
profiles.Chrome_144
profiles.Chrome_144_PSK
profiles.Chrome_133
profiles.Chrome_133_PSK

// Older versions
profiles.Chrome_131
profiles.Chrome_130_PSK
profiles.Chrome_124
profiles.Chrome_120
// ... and more
PSK (Pre-Shared Key) variants support TLS session resumption, which is more realistic for simulating returning users.

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Firefox profiles

profiles.Firefox_147
profiles.Firefox_147_PSK
profiles.Firefox_146_PSK
profiles.Firefox_135
profiles.Firefox_133
profiles.Firefox_132
// ... and more

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Safari profiles

// Desktop Safari
profiles.Safari_16_0
profiles.Safari_15_6_1

// iOS Safari
profiles.Safari_IOS_26_0
profiles.Safari_IOS_18_5
profiles.Safari_IOS_18_0
profiles.Safari_IOS_17_0
profiles.Safari_IOS_16_0

// iPad Safari
profiles.Safari_Ipad_15_6

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Other browsers

// Opera
profiles.Opera_91
profiles.Opera_90
profiles.Opera_89

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Anatomy of a client profile

Each profile is a structured configuration defined in profiles/profiles.go:89: 
type ClientProfile struct {
    clientHelloId          tls.ClientHelloID
    headerPriority         *http2.PriorityParam
    settings               map[http2.SettingID]uint32
    settingsOrder          []http2.SettingID
    priorities             []http2.Priority
    pseudoHeaderOrder      []string
    connectionFlow         uint32
    streamID               uint32
    allowHTTP              bool
    http3Settings          map[uint64]uint64
    http3SettingsOrder     []uint64
    http3PriorityParam     uint32
    http3PseudoHeaderOrder []string
    http3SendGreaseFrames  bool
}

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TLS layer

The clientHelloId defines the TLS fingerprint: 
clientHelloId: tls.ClientHelloID{
    Client:  "Chrome",
    Version: "146_PSK",
    SpecFactory: func() (tls.ClientHelloSpec, error) {
        return tls.ClientHelloSpec{
            CipherSuites: []uint16{
                tls.GREASE_PLACEHOLDER,
                tls.TLS_AES_128_GCM_SHA256,
                tls.TLS_AES_256_GCM_SHA384,
                tls.TLS_CHACHA20_POLY1305_SHA256,
                // ...
            },
            Extensions: []tls.TLSExtension{
                &tls.UtlsGREASEExtension{},
                &tls.ApplicationSettingsExtensionNew{},
                &tls.SupportedVersionsExtension{},
                // ...
            },
        }, nil
    },
}
GREASE (Generate Random Extensions And Sustain Extensibility) values are random placeholders that prevent fingerprint ossification. Chrome uses them, Firefox doesn’t.

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HTTP/2 layer

HTTP/2 settings define frame parameters: 
settings: map[http2.SettingID]uint32{
    http2.SettingHeaderTableSize:   65536,
    http2.SettingEnablePush:        0,
    http2.SettingInitialWindowSize: 6291456,
    http2.SettingMaxHeaderListSize: 262144,
},
settingsOrder: []http2.SettingID{
    http2.SettingHeaderTableSize,
    http2.SettingEnablePush,
    http2.SettingInitialWindowSize,
    http2.SettingMaxHeaderListSize,
},
pseudoHeaderOrder: []string{
    ":method",
    ":authority",
    ":scheme",
    ":path",
},
connectionFlow: 15663105,
The order of settings and pseudo-headers is as important as the values themselves for accurate fingerprinting.

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HTTP/3 layer

HTTP/3 profiles include QUIC-specific settings: 
http3Settings: map[uint64]uint64{
    0x01: 8,      // SETTINGS_MAX_FIELD_SECTION_SIZE
    0x06: 262144, // SETTINGS_MAX_HEADER_LIST_SIZE
    0x33: 1,      // H3_DATAGRAM
},
http3SettingsOrder: []uint64{0x01, 0x06, 0x33},
http3PriorityParam: 3,
http3SendGreaseFrames: true,
http3PseudoHeaderOrder: []string{
    ":method",
    ":authority",
    ":scheme",
    ":path",
},

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Using profiles

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Basic usage

import (
    tls_client "github.com/bogdanfinn/tls-client"
    "github.com/bogdanfinn/tls-client/profiles"
)

client, err := tls_client.NewHttpClient(tls_client.NewNoopLogger(),
    tls_client.WithClientProfile(profiles.Chrome_146),
)
if err != nil {
    log.Fatal(err)
}

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Dynamic profile selection

Select profiles at runtime based on string identifiers: 
profileName := "chrome_146" // from config or user input

profile, exists := profiles.MappedTLSClients[profileName]
if !exists {
    profile = profiles.DefaultClientProfile // Chrome_133
}

client, err := tls_client.NewHttpClient(tls_client.NewNoopLogger(),
    tls_client.WithClientProfile(profile),
)
Available string identifiers are defined in profiles/profiles.go:10: 
var MappedTLSClients = map[string]ClientProfile{
    "chrome_146":          Chrome_146,
    "chrome_146_PSK":      Chrome_146_PSK,
    "firefox_147":         Firefox_147,
    "safari_ios_26_0":     Safari_IOS_26_0,
    // ...
}

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Browser differences

Different browsers have distinct fingerprinting characteristics:

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Chrome characteristics

  • Uses GREASE extensions and values
  • Supports HTTP/3 with specific QUIC settings
  • Sends H3_DATAGRAM setting (0x33)
  • Includes MLKEM768 post-quantum key exchange
  • Uses Brotli certificate compression

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Firefox characteristics

  • No GREASE in TLS handshake
  • Different cipher suite ordering
  • Sends GREASE frames in HTTP/3 but not GREASE settings
  • Doesn’t send SETTINGS_MAX_FIELD_SECTION_SIZE in HTTP/3
  • Different HTTP/2 priority scheme

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Safari characteristics

  • Unique TLS extension ordering
  • iOS vs desktop variations
  • Different supported curves
  • Specific HTTP/2 window sizes
Mixing incompatible settings (e.g., Chrome TLS with Firefox HTTP/2 settings) creates detectable anomalies. Always use complete, tested profiles.

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Choosing the right profile

Consider these factors when selecting a profile:
  1. Target website - Match the most common visitor browser
  2. Geographic region - Chrome dominates globally, but Safari is significant in iOS-heavy markets
  3. Update frequency - Newer versions may be less widely deployed
  4. Session resumption - Use PSK variants for multi-request scenarios
// For general web scraping
profiles.Chrome_144  // Widely deployed, stable fingerprint

// For iOS-specific targets
profiles.Safari_IOS_18_5  // Latest stable iOS Safari

// For session persistence
profiles.Chrome_146_PSK  // With TLS session resumption
Monitor your target website’s legitimate traffic to understand which browser versions are most common, then match those profiles.

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Profile updates

Browser fingerprints change with each browser release. The library is updated to include:
  • New browser versions as they’re released
  • Changes to TLS extensions and cipher suites
  • Updated HTTP/2 and HTTP/3 parameters
  • New features like post-quantum cryptography
Check the GitHub repository for the latest profile updates.

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Custom profiles

For advanced use cases, you can create custom profiles: 
customProfile := profiles.NewClientProfile(
    customClientHelloId,
    customHTTP2Settings,
    customSettingsOrder,
    customPseudoHeaderOrder,
    customConnectionFlow,
    customPriorities,
    customHeaderPriority,
    customStreamID,
    allowHTTP,
    customHTTP3Settings,
    customHTTP3SettingsOrder,
    customHTTP3PriorityParam,
    customHTTP3PseudoHeaderOrder,
    customHTTP3SendGreaseFrames,
)
Creating custom profiles requires deep knowledge of TLS, HTTP/2, and HTTP/3 specifications. Incorrect configurations will be easily detected.

TLS fingerprinting

Learn about TLS fingerprinting basics

HTTP protocols

Understand protocol support and negotiation

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