Root certificate · Let's Encrypt
ISRG Root X1
ISRG Root X1 is a root CA certificate operated by Let's Encrypt (RSA 4096, valid until 2035-06-04, SHA-256 96BCEC06). As of the latest CCADB data it is trusted for TLS server authentication by 4 of 4 major root stores: Chrome, Mozilla, Apple, Microsoft.
Root store status
| Root store | Status | Trusted for TLS | Distrust for TLS after | Constrained |
|---|---|---|---|---|
| Chrome | Included Included | Yes | — | No |
| Mozilla | Included Included | Yes | — | No |
| Apple | Included Included | Yes | — | Yes |
| Microsoft | Included Included | Yes | — | No |
The CCADB lists no EV policy OID for ISRG Root X1.
Included Chrome
- Status
- Included
Included Mozilla
- Status
- Included
- Trust bits
- Websites
- EV policy OIDs
- not EV-enabled
- First included in
- NSS 3.26 / Firefox 50
- Inclusion bug
- #1204656
Included Apple
- Status
- Included
- Trust bits
- serverAuth, clientAuth
- Allowed policies
- Server Authentication, Client Authentication, Code Signing, Timestamp Signing
Included Microsoft
- Status
- Included
- Trusted EKUs
- Server Authentication, Client Authentication
"Trusted for TLS" means the store includes the root with the server-authentication trust bit (Mozilla "Websites", Apple serverAuth, Microsoft Server Authentication EKU). Microsoft "NotBefore" means only certificates issued before a cutoff date are still trusted. "Constrained" means the store applies extra restrictions.
Details
- CA owner
- Internet Security Research Group
- Subject
- CN=ISRG Root X1,O=Internet Security Research Group,C=US
- SHA-256
96BCEC06264976F37460779ACF28C5A7CFE8A3C0AAE11A8FFCEE05C0BDDF08C6- SHA-1 (Windows thumbprint)
CABD2A79A1076A31F21D253635CB039D4329A5E8- SPKI SHA-256
0B9FA5A59EED715C26C1020C711B4F6EC42D58B0015E14337A39DAD301C5AFC3- Valid from
- 2015-06-04
- Expires
- 2035-06-04
- Key
- RSA 4096
- Signature algorithm
- sha256WithRSAEncryption
- Serial number
8210CFB0D240E3594463E0BB63828B00- Country
- US
- Trust bits (CCADB)
- Server Authentication, Client Authentication
- EV policy OIDs (CCADB)
- not EV-enabled · TLS EV capable: No
- Test websites
- valid:
https://valid.x1.test-certs.letsencrypt.org/· expired:https://expired.x1.test-certs.letsencrypt.org/· revoked:https://revoked.x1.test-certs.letsencrypt.org/ - CCADB record
- A003754
- PEM
- lets-encrypt-isrg-root-x1.pem
Intermediate CAs issued by this root
The CCADB lists 21 intermediate CA certificates signed directly by ISRG Root X1: 12 currently valid, 7 expired and 2 revoked (revoked includes those whose parent was revoked).
Showing 20 of 21: valid certificates first, newest first. Each name links to its crt.sh entry by SHA-256; an arrow marks a cross-certificate for another root on this site.
| Intermediate | Operated by | Expires | Status |
|---|---|---|---|
| ISRG Root X2 → ISRG Root X2 | Internet Security Research Group | 2032-09-02 | Valid |
| Root YR | Internet Security Research Group | 2032-09-02 | Valid |
| E9 | Internet Security Research Group | 2027-03-12 | Valid |
| R13 | Internet Security Research Group | 2027-03-12 | Valid |
| E7 | Internet Security Research Group | 2027-03-12 | Valid |
| R10 | Internet Security Research Group | 2027-03-12 | Valid |
| E8 | Internet Security Research Group | 2027-03-12 | Valid |
| E6 | Internet Security Research Group | 2027-03-12 | Valid |
| E5 | Internet Security Research Group | 2027-03-12 | Valid |
| R11 | Internet Security Research Group | 2027-03-12 | Valid |
| R14 | Internet Security Research Group | 2027-03-12 | Valid |
| R12 | Internet Security Research Group | 2027-03-12 | Valid |
| ISRG Root X2 → ISRG Root X2 | Internet Security Research Group | 2025-09-15 | Expired |
| R3 | Internet Security Research Group | 2025-09-15 | Expired |
| R4 | Internet Security Research Group | 2025-09-15 | Expired |
| Let's Encrypt Authority X3 | Internet Security Research Group | 2021-10-06 | Expired |
| Let's Encrypt Authority X4 | Internet Security Research Group | 2021-10-06 | Expired |
| Let's Encrypt Authority X2 | Internet Security Research Group | 2020-06-04 | Expired |
| Let's Encrypt Authority X1 | Internet Security Research Group | 2020-06-04 | Expired |
| Root YR | Internet Security Research Group | 2032-09-02 | Revoked |
Cross-signed versions
1 certificate(s) in the CCADB have the same subject and public key as ISRG Root X1 but a different issuer. A server can send one of them so that clients which trust the issuing root, but not ISRG Root X1, can still build a chain.
| Signed by | CA owner | Expires | Status |
|---|---|---|---|
| DST Root CA X3 crt.sh | IdenTrust Services, LLC | 2024-09-30 | Expired |
CRL and OCSP addresses
In the root certificate
ISRG Root X1 itself contains no CRL Distribution Points and no OCSP (Authority Information Access) extension. That is normal for a root: clients trust it directly and do not check its own revocation status.
Full CRL this CA publishes (CCADB)
http://x1.c.lencr.org/
Used by the intermediates it issued
Addresses found in the CRL Distribution Points and OCSP fields of the 12 valid intermediates signed by ISRG Root X1; the number in brackets is how many of them use each address.
- CRL:
http://x1.c.lencr.org/(12)
None of the valid intermediates under this root lists an OCSP responder.
What happens when it expires
ISRG Root X1 is valid until 2035-06-04, about 8.6 years after this data snapshot (2026-11-10). From that day, browsers and operating systems that check trust-anchor expiry stop accepting chains that end at this root, so any certificate that can only chain to it fails validation. Android is a known exception: it does not enforce the expiry date of trust anchors.
Check whether your device trusts it
Each platform keeps its own root store. The commands below look up ISRG Root X1 by common name (ISRG Root X1) or fingerprint. The store status in each heading comes from the CCADB snapshot; your device can differ if it is out of date or managed by an administrator.
macOS (Apple store: Included · Trusted for TLS)
Search the system roots keychain by common name. -Z prints the SHA-256 hash, which must match the fingerprint on the last line.
security find-certificate -a -c "ISRG Root X1" -Z \
/System/Library/Keychains/SystemRootCertificates.keychain | grep "SHA-256"
# SHA-256 hash: 96BCEC06264976F37460779ACF28C5A7CFE8A3C0AAE11A8FFCEE05C0BDDF08C6Windows (Microsoft store: Included · Trusted for TLS)
Windows identifies roots by SHA-1 thumbprint. It installs third-party roots on demand through Automatic Root Certificates Update, so "not found" can also mean the root has not been needed yet; certutil -generateSSTFromWU roots.sst downloads Microsoft's full list.
certutil -verifystore Root CABD2A79A1076A31F21D253635CB039D4329A5E8Linux (ca-certificates follows Mozilla: Included · Trusted for TLS)
Debian, Ubuntu, Fedora and RHEL build their ca-certificates package from Mozilla's root store. Use trust list on p11-kit systems, or search the PEM bundle on Debian and Ubuntu.
# Fedora / RHEL / Arch (p11-kit)
trust list --filter=ca-anchors | grep -iF -A2 "ISRG Root X1"
# Debian / Ubuntu (ca-certificates)
openssl crl2pkcs7 -nocrl -certfile /etc/ssl/certs/ca-certificates.crt \
| openssl pkcs7 -print_certs -noout | grep -iF "ISRG Root X1"Java
Java ships its own cacerts keystore; JDK 9 and later accept -cacerts and the default store password is changeit. Search for the SHA-256 fingerprint in colon form.
keytool -list -cacerts -storepass changeit | grep -i "96:BC:EC:06:26:49:76:F3:74:60:77:9A:CF:28:C5:A7:CF:E8:A3:C0:AA:E1:1A:8F:FC:EE:05:C0:BD:DF:08:C6"Android
Android's system store is maintained by Google separately from the four CCADB stores above. Open Settings → Security & privacy → More security settings → Encryption & credentials → Trusted credentials → System (menu names vary by vendor and version) and look for Internet Security Research Group → ISRG Root X1.
Which root does my site chain to?
List the chain your server sends and compare the last issuer with this root; the fingerprint check confirms a local copy.
# show subject (s:) and issuer (i:) of every certificate the server sends
openssl s_client -connect example.com:443 -servername example.com -showcerts </dev/null 2>/dev/null \
| grep -E '^ *[0-9]+ s:|^ *i:'
# subject and SHA-256 fingerprint of the downloaded PEM file
openssl x509 -in lets-encrypt-isrg-root-x1.pem -noout -subject -fingerprint -sha256
# sha256 Fingerprint=96:BC:EC:06:26:49:76:F3:74:60:77:9A:CF:28:C5:A7:CF:E8:A3:C0:AA:E1:1A:8F:FC:EE:05:C0:BD:DF:08:C6FAQ
Is ISRG Root X1 trusted by Chrome, Firefox, Safari and Windows?
Yes. As of 2026-11-10, Chrome, Mozilla (Firefox), Apple (Safari) and Microsoft (Windows) all trust it for TLS server authentication.
When does ISRG Root X1 expire?
On 2035-06-04, about 8.6 years after the 2026-11-10 data snapshot.
How many intermediate certificates has ISRG Root X1 issued?
The CCADB lists 21: 12 valid, 7 expired and 2 revoked. The newest valid one is ISRG Root X2, valid until 2032-09-02.
Is ISRG Root X1 cross-signed?
Yes. The CCADB has 1 cross-certificate(s) with its subject and key, signed by DST Root CA X3; 0 of them are still valid.
Other roots from Let's Encrypt
- ISRG Root X2 ECDSA P-384 · 2040-09-17
Sources
- CCADB — Resources (TLS Server Authentication report, All Included Root Certificate Trust Bit Settings)
- CCADB — All Certificate Information (root and intermediate), CSV V5
- CCADB — Mozilla Included CA Certificate Report
- CCADB — Chrome / Mozilla / Apple / Microsoft TLS Server Authentication CSV