An Object Identifier (OID) is a dot-separated sequence of numbers used to uniquely identify various objects within the WebPKI. For example, every extension within an X.509 certificate is uniquely identified by an OID, and the OID 2.5.29.15 identifies the Key Usage extension. Similarly, the OID 2.23.140.1.2.1 can be placed within the body of the Certificate Policies extension to indicate that the certificate was validated according to the CA/Browser Forum’s “Domain Validated” criteria.
This page lists the OIDs used by Let’s Encrypt, documents what each OID means, and points to where we use them.
| OID | Description |
|---|---|
1.3.6.1.4.1.44947 |
Internet Security Research Group. Parent arc for all ISRG OIDs. |
1.3.6.1.4.1.44947.1 |
No meaning assigned. This legacy OID never had a standalone purpose. |
1.3.6.1.4.1.44947.1.1 |
No meaning assigned. This legacy OID never had a standalone purpose. |
1.3.6.1.4.1.44947.1.1.1 |
ISRG Domain Validated. This legacy OID was equivalent to 2.23.140.1.2.1, the CA/BF Domain Validated Certificate Policy OID. We used to include it in our issuing intermediates, but stopped doing so to reduce certificate size. |
1.3.6.1.4.1.44947.2 |
Let’s Encrypt Trust Anchor IDs. Parent arc for all “trust anchors” (CA keypairs), which can be used in the Trust Anchor Identifiers and Merkle Tree Certificates internet draft standards. OIDs in this arc are assigned approximately chronologically by issuance date. |
1.3.6.1.4.1.44947.2.1 |
ISRG Root X1 |
1.3.6.1.4.1.44947.2.2 |
Let’s Encrypt Authority X1 |
1.3.6.1.4.1.44947.2.3 |
Let’s Encrypt Authority X2 |
1.3.6.1.4.1.44947.2.4 |
Let’s Encrypt Authority X3 |
1.3.6.1.4.1.44947.2.5 |
Let’s Encrypt Authority X4 |
1.3.6.1.4.1.44947.2.6 |
ISRG Root X2 |
1.3.6.1.4.1.44947.2.7 |
Let’s Encrypt E1 |
1.3.6.1.4.1.44947.2.8 |
Let’s Encrypt E2 |
1.3.6.1.4.1.44947.2.9 |
Let’s Encrypt R3 |
1.3.6.1.4.1.44947.2.10 |
Let’s Encrypt R4 |
1.3.6.1.4.1.44947.2.11 |
Let’s Encrypt E5 |
1.3.6.1.4.1.44947.2.12 |
Let’s Encrypt E6 |
1.3.6.1.4.1.44947.2.13 |
Let’s Encrypt E7 |
1.3.6.1.4.1.44947.2.14 |
Let’s Encrypt E8 |
1.3.6.1.4.1.44947.2.15 |
Let’s Encrypt E9 |
1.3.6.1.4.1.44947.2.16 |
Let’s Encrypt R10 |
1.3.6.1.4.1.44947.2.17 |
Let’s Encrypt R11 |
1.3.6.1.4.1.44947.2.18 |
Let’s Encrypt R12 |
1.3.6.1.4.1.44947.2.19 |
Let’s Encrypt R13 |
1.3.6.1.4.1.44947.2.20 |
Let’s Encrypt R14 |
1.3.6.1.4.1.44947.2.21 |
ISRG Root YE |
1.3.6.1.4.1.44947.2.22 |
ISRG Root YR |
1.3.6.1.4.1.44947.2.23 |
Let’s Encrypt YE1 |
1.3.6.1.4.1.44947.2.24 |
Let’s Encrypt YE2 |
1.3.6.1.4.1.44947.2.25 |
Let’s Encrypt YE3 |
1.3.6.1.4.1.44947.2.26 |
Let’s Encrypt YR1 |
1.3.6.1.4.1.44947.2.27 |
Let’s Encrypt YR2 |
1.3.6.1.4.1.44947.2.28 |
Let’s Encrypt YR3 |