Compare
CRT vs PEM
CRT is a filename extension commonly used for certificates. PEM is a text encoding that can contain certificates, keys, or related objects; they are not equivalent categories.
Which format should you choose?
Check the deployment target's required extension and encoding; inspect whether a CRT file is PEM or DER and whether a chain is included.
Good fit for CRT
Transfer or deploy X.509 certificates
- Servers and clients requesting certificate files
Good fit for PEM
Represent certificates and keys as text
- Systems requesting PEM-encoded material
Basic information
| Field | CRT | PEM |
|---|---|---|
| Extension | .crt, .cer | .pem |
| MIME type | application/pkix-cert | application/x-pem-file |
| Common uses | Transfer or deploy X.509 certificates | Represent certificates and keys as text |
| How to open | Use a certificate viewer to inspect subject names, issuer, validity dates, and chain. | Inspect the labels as text without pasting the contents into public chats or shared locations. |
| Export or convert | Before converting, determine encoding, whether the file includes a chain, and whether a private key is stored separately. | Before converting to DER or PKCS#12, identify the contained objects and whether a private key must be handled. |
Choose by use case
Servers and clients requesting certificate files
Transfer or deploy X.509 certificates
CRTSystems requesting PEM-encoded material
Represent certificates and keys as text
PEMKey point 1
CRT commonly labels a certificate file.
More on the differencesKey point 2
PEM describes an encoded text representation, not a certificate-only extension.
More on the differencesMore on the differences
Inspect the file contents and target configuration before deployment. Handle private-key material separately and do not assume that renaming changes the encoding.
- A .crt file may contain PEM-encoded certificate data.
- PEM can represent certificates and other cryptographic objects.
- The expected chain and encoding depend on the server or tool.
Frequently asked questions
Can a CRT file also be PEM?
Yes. The extension and internal encoding are separate properties; inspect the file and deployment requirements.