Recommended configurations

The Mozilla SSL Configuration Generator Mozilla maintains three recommended configurations for servers using TLS. Pick the correct configuration depending on your audience:

• Modern: Modern clients that support TLS 1.3, with no need for backwards compatibility
• Intermediate: Recommended configuration for a general-purpose server
• Old: Services accessed by very old clients or libraries, such as Internet Explorer 8 (Windows XP), Java 6, or OpenSSL 0.9.8

The ordering of cipher suites in the Old configuration is very important, as it determines the priority with which algorithms are selected.

OpenSSL will ignore cipher suites it doesn't understand, so always use the full set of cipher suites below, in their recommended order. The use of the Old configuration with modern versions of OpenSSL may require custom builds with support for deprecated ciphers.

Modern compatibility

For services with clients that support TLS 1.3 and don't need backward compatibility, the Modern configuration provides an extremely high level of security.

• Cipher suites (TLS 1.3): TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256
• Cipher suites (TLS 1.2): (none)
• Protocols: TLS 1.3
• Certificate type: ECDSA (P-256)
• TLS curves: X25519, prime256v1, secp384r1
• HSTS: max-age=63072000 (two years)
• Certificate lifespan: 90 days
• Cipher preference: client chooses

0x13,0x01  -  TLS_AES_128_GCM_SHA256        TLSv1.3  Kx=any  Au=any  Enc=AESGCM(128)             Mac=AEAD
0x13,0x02  -  TLS_AES_256_GCM_SHA384        TLSv1.3  Kx=any  Au=any  Enc=AESGCM(256)             Mac=AEAD
0x13,0x03  -  TLS_CHACHA20_POLY1305_SHA256  TLSv1.3  Kx=any  Au=any  Enc=CHACHA20/POLY1305(256)  Mac=AEAD

• Rationale:
  • All cipher suites are forward secret and authenticated
  • The cipher suites are all strong and so we allow the client to choose, as they will know best if they have support for hardware-accelerated AES
  • We recommend ECDSA certificates using P-256, as P-384 provides negligible improvements to security and Ed25519 is not yet widely supported

Intermediate compatibility (recommended)

For services that don't need compatibility with legacy clients such as Windows XP or old versions of OpenSSL. This is the recommended configuration for the vast majority of services, as it is highly secure and compatible with nearly every client released in the last five (or more) years.

• Cipher suites (TLS 1.3): TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256
• Cipher suites (TLS 1.2): ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305
• Protocols: TLS 1.2, TLS 1.3
• TLS curves: X25519, prime256v1, secp384r1
• Certificate type: ECDSA (P-256) (recommended), or RSA (2048 bits)
• DH parameter size: 2048 (ffdhe2048, RFC 7919)
• HSTS: max-age=63072000 (two years)
• Certificate lifespan: 90 days (recommended) to 366 days
• Cipher preference: client chooses

0x13,0x01  -  TLS_AES_128_GCM_SHA256         TLSv1.3  Kx=any   Au=any    Enc=AESGCM(128)             Mac=AEAD
0x13,0x02  -  TLS_AES_256_GCM_SHA384         TLSv1.3  Kx=any   Au=any    Enc=AESGCM(256)             Mac=AEAD
0x13,0x03  -  TLS_CHACHA20_POLY1305_SHA256   TLSv1.3  Kx=any   Au=any    Enc=CHACHA20/POLY1305(256)  Mac=AEAD
0xC0,0x2B  -  ECDHE-ECDSA-AES128-GCM-SHA256  TLSv1.2  Kx=ECDH  Au=ECDSA  Enc=AESGCM(128)             Mac=AEAD
0xC0,0x2F  -  ECDHE-RSA-AES128-GCM-SHA256    TLSv1.2  Kx=ECDH  Au=RSA    Enc=AESGCM(128)             Mac=AEAD
0xC0,0x2C  -  ECDHE-ECDSA-AES256-GCM-SHA384  TLSv1.2  Kx=ECDH  Au=ECDSA  Enc=AESGCM(256)             Mac=AEAD
0xC0,0x30  -  ECDHE-RSA-AES256-GCM-SHA384    TLSv1.2  Kx=ECDH  Au=RSA    Enc=AESGCM(256)             Mac=AEAD
0xCC,0xA9  -  ECDHE-ECDSA-CHACHA20-POLY1305  TLSv1.2  Kx=ECDH  Au=ECDSA  Enc=CHACHA20/POLY1305(256)  Mac=AEAD
0xCC,0xA8  -  ECDHE-RSA-CHACHA20-POLY1305    TLSv1.2  Kx=ECDH  Au=RSA    Enc=CHACHA20/POLY1305(256)  Mac=AEAD
0x00,0x9E  -  DHE-RSA-AES128-GCM-SHA256      TLSv1.2  Kx=DH    Au=RSA    Enc=AESGCM(128)             Mac=AEAD
0x00,0x9F  -  DHE-RSA-AES256-GCM-SHA384      TLSv1.2  Kx=DH    Au=RSA    Enc=AESGCM(256)             Mac=AEAD
0xCC,0xAA  -  DHE-RSA-CHACHA20-POLY1305      TLSv1.2  Kx=DH    Au=RSA    Enc=CHACHA20/POLY1305(256)  Mac=AEAD

• Rationale:
  • All cipher suites are forward secret and authenticated
  • TLS 1.2 is the minimum supported protocol, as recommended by RFC 7525, PCI DSS, and others
  • ECDSA certificates are recommended over RSA certificates, as they allow the use of ECDHE with Windows 7 clients using Internet Explorer 11, as well as allow connections from IE11 on Windows Server 2008 R2
  • The cipher suites are all strong and so we allow the client to choose, as they will know best if they have support for hardware-accelerated AES
  • Windows XP (including all embedded versions) are no longer supported by Microsoft, eliminating the need for many older protocols and ciphers
  • Administrators needing to provide access to IE 11 on Windows Server 2008 R2 and who are unable to switch to or add ECDSA certificates can add TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
  • While the goal is to support a broad range of clients, we reasonably disable a number of ciphers that have little support (such as ARIA, Camellia, 3DES, and SEED)
  • 90 days is the recommended maximum certificate lifespan, to encourage certificate issuance automation

Old backward compatibility

This configuration is compatible with a number of very old clients, and should be used only as a last resort.

• Cipher suites (TLS 1.3): TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256
• Cipher suites (TLS 1.0 - 1.2): ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA
• Protocols: TLS 1.0, TLS 1.1, TLS 1.2, TLS 1.3
• TLS curves: X25519, prime256v1, secp384r1
• Certificate type: RSA (2048-bits)
• Certificate curve: None
• DH parameter size: 1024 (generated with openssl dhparam 1024)
• HSTS: max-age=63072000 (two years)
• Certificate lifespan: 90 days (recommended) to 366 days
• Cipher preference: server chooses

0x13,0x01  -  TLS_AES_128_GCM_SHA256         TLSv1.3  Kx=any   Au=any    Enc=AESGCM(128)             Mac=AEAD
0x13,0x02  -  TLS_AES_256_GCM_SHA384         TLSv1.3  Kx=any   Au=any    Enc=AESGCM(256)             Mac=AEAD
0x13,0x03  -  TLS_CHACHA20_POLY1305_SHA256   TLSv1.3  Kx=any   Au=any    Enc=CHACHA20/POLY1305(256)  Mac=AEAD
0xC0,0x2B  -  ECDHE-ECDSA-AES128-GCM-SHA256  TLSv1.2  Kx=ECDH  Au=ECDSA  Enc=AESGCM(128)             Mac=AEAD
0xC0,0x2F  -  ECDHE-RSA-AES128-GCM-SHA256    TLSv1.2  Kx=ECDH  Au=RSA    Enc=AESGCM(128)             Mac=AEAD
0xC0,0x2C  -  ECDHE-ECDSA-AES256-GCM-SHA384  TLSv1.2  Kx=ECDH  Au=ECDSA  Enc=AESGCM(256)             Mac=AEAD
0xC0,0x30  -  ECDHE-RSA-AES256-GCM-SHA384    TLSv1.2  Kx=ECDH  Au=RSA    Enc=AESGCM(256)             Mac=AEAD
0xCC,0xA9  -  ECDHE-ECDSA-CHACHA20-POLY1305  TLSv1.2  Kx=ECDH  Au=ECDSA  Enc=CHACHA20/POLY1305(256)  Mac=AEAD
0xCC,0xA8  -  ECDHE-RSA-CHACHA20-POLY1305    TLSv1.2  Kx=ECDH  Au=RSA    Enc=CHACHA20/POLY1305(256)  Mac=AEAD
0x00,0x9E  -  DHE-RSA-AES128-GCM-SHA256      TLSv1.2  Kx=DH    Au=RSA    Enc=AESGCM(128)             Mac=AEAD
0x00,0x9F  -  DHE-RSA-AES256-GCM-SHA384      TLSv1.2  Kx=DH    Au=RSA    Enc=AESGCM(256)             Mac=AEAD
0xCC,0xAA  -  DHE-RSA-CHACHA20-POLY1305      TLSv1.2  Kx=DH    Au=RSA    Enc=CHACHA20/POLY1305(256)  Mac=AEAD
0xC0,0x23  -  ECDHE-ECDSA-AES128-SHA256      TLSv1.2  Kx=ECDH  Au=ECDSA  Enc=AES(128)                Mac=SHA256
0xC0,0x27  -  ECDHE-RSA-AES128-SHA256        TLSv1.2  Kx=ECDH  Au=RSA    Enc=AES(128)                Mac=SHA256
0xC0,0x09  -  ECDHE-ECDSA-AES128-SHA         TLSv1    Kx=ECDH  Au=ECDSA  Enc=AES(128)                Mac=SHA1
0xC0,0x13  -  ECDHE-RSA-AES128-SHA           TLSv1    Kx=ECDH  Au=RSA    Enc=AES(128)                Mac=SHA1
0xC0,0x24  -  ECDHE-ECDSA-AES256-SHA384      TLSv1.2  Kx=ECDH  Au=ECDSA  Enc=AES(256)                Mac=SHA384
0xC0,0x28  -  ECDHE-RSA-AES256-SHA384        TLSv1.2  Kx=ECDH  Au=RSA    Enc=AES(256)                Mac=SHA384
0xC0,0x0A  -  ECDHE-ECDSA-AES256-SHA         TLSv1    Kx=ECDH  Au=ECDSA  Enc=AES(256)                Mac=SHA1
0xC0,0x14  -  ECDHE-RSA-AES256-SHA           TLSv1    Kx=ECDH  Au=RSA    Enc=AES(256)                Mac=SHA1
0x00,0x67  -  DHE-RSA-AES128-SHA256          TLSv1.2  Kx=DH    Au=RSA    Enc=AES(128)                Mac=SHA256
0x00,0x6B  -  DHE-RSA-AES256-SHA256          TLSv1.2  Kx=DH    Au=RSA    Enc=AES(256)                Mac=SHA256
0x00,0x9C  -  AES128-GCM-SHA256              TLSv1.2  Kx=RSA   Au=RSA    Enc=AESGCM(128)             Mac=AEAD
0x00,0x9D  -  AES256-GCM-SHA384              TLSv1.2  Kx=RSA   Au=RSA    Enc=AESGCM(256)             Mac=AEAD
0x00,0x3C  -  AES128-SHA256                  TLSv1.2  Kx=RSA   Au=RSA    Enc=AES(128)                Mac=SHA256
0x00,0x3D  -  AES256-SHA256                  TLSv1.2  Kx=RSA   Au=RSA    Enc=AES(256)                Mac=SHA256
0x00,0x2F  -  AES128-SHA                     SSLv3    Kx=RSA   Au=RSA    Enc=AES(128)                Mac=SHA1
0x00,0x35  -  AES256-SHA                     SSLv3    Kx=RSA   Au=RSA    Enc=AES(256)                Mac=SHA1
0x00,0x0A  -  DES-CBC3-SHA                   SSLv3    Kx=RSA   Au=RSA    Enc=3DES(168)               Mac=SHA1

• Rationale:
  • Take a hard look at your infrastructure needs before using this configuration; it is intended for special use cases only
  • If possible, use this configuration only for endpoints that require it, segregating it from other traffic
  • SSLv3 has been disabled entirely, ending support for older Windows XP SP2 clients. Users requiring support for Windows XP SP2 may use previous versions of this configuration, with the caveat that SSLv3 is no longer safe to use
  • This configuration requires custom builds to work with modern versions of OpenSSL, using enable-ssl3, enable-ssl3-method, enable-deprecated, and enable-weak-ssl-ciphers
  • Most ciphers that are not clearly broken and dangerous to use are supported

JSON version of the recommendations

Mozilla also maintains these recommendations in JSON format, for automated system configuration. This location is versioned and permanent, and can be referenced in scripts and tools. The file will not change, to avoid breaking tools when we update the recommendations.

We also maintain a rolling version of these recommendations, with the caveat that they may change without warning and without providing backwards compatibility. As it may break things if you use it to automatically configure your servers without review, we recommend you use the version-specific file instead.

Version History