Is my .cer file DER or PEM?

Open it in a text editor. If it starts with -----BEGIN CERTIFICATE-----, it is already PEM; if it shows unreadable binary characters, it is DER. This converter accepts both and always outputs PEM, so you do not need to check first.

What is the OpenSSL equivalent?

openssl x509 -inform der -in certificate.cer -out certificate.pem converts a DER certificate. This converter produces the same PEM: the certificate Base64-encoded in 64-character lines between BEGIN/END CERTIFICATE markers.

Can I convert a private key with this tool?

No, and you should never upload a private key to an online tool. Certificates are public by design, so converting them is safe; private keys are not.

How do I convert CER to PEM?

Upload your CER file above, click Convert, and download the PEM result instantly. No account or software needed.

Is converting CER to PEM free?

Yes. It is free and unlimited for files up to 5 MB, with no account required. Larger files get 3 free conversions per day; beyond that, credit packs start at $1 and credits never expire.

Are my files stored or shared?

No. Files are processed in server memory and deleted immediately after conversion. Nothing is written to disk or retained.

Do I need to install anything?

No software installation needed. OmniConvert runs in the browser — just upload, convert, and download.

OmniConvert

Convert CER to PEM

Free

Free and unlimited

For files up to 5 MB. No account needed. Larger files: 3 free per day.

Related Security conversions

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Convert JWT to JSON (decode)— Decode a JWT token and extract the header and payload as JSON — no verification, client-safe
Convert X.509 certificate to JSON— Decode an X.509 certificate (PEM or DER) and extract fields as JSON
Convert SSH public key to JSON— Parse an SSH public key and extract its type, fingerprint, and key info as JSON
Convert CSR to JSON— Decode a PEM certificate signing request (CSR) and extract subject and metadata as JSON

About this conversion

Convert a .cer certificate (DER or PEM encoded) to a PEM file. This converter processes your CER file server-side and returns a PEM file instantly — no account, no software installation, and no file storage. Files are deleted from our servers immediately after conversion.

Learn more: PEM / DER / CER / CRT file format explained

How to convert CER to PEM

1. Upload — drag your CER file onto the converter above, or click to browse.
2. Convert — press Convert. Processing happens on secure servers in seconds.
3. Download — your PEM file downloads automatically. No sign-up required.

Convert CER to PEM from the command line

curl --fail-with-body \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -F "file=@input.cer" \
  -F "conversionId=cer-to-pem" \
  https://www.omniconvert.cloud/api/convert -o output.pem

The API needs a token from a credit pack, and each API conversion uses one credit. Converting on this page stays free. API documentation

Frequently Asked Questions

Is my .cer file DER or PEM?: Open it in a text editor. If it starts with -----BEGIN CERTIFICATE-----, it is already PEM; if it shows unreadable binary characters, it is DER. This converter accepts both and always outputs PEM, so you do not need to check first.
What is the OpenSSL equivalent?: openssl x509 -inform der -in certificate.cer -out certificate.pem converts a DER certificate. This converter produces the same PEM: the certificate Base64-encoded in 64-character lines between BEGIN/END CERTIFICATE markers.
Can I convert a private key with this tool?: No, and you should never upload a private key to an online tool. Certificates are public by design, so converting them is safe; private keys are not.
How do I convert CER to PEM?: Upload your CER file above, click Convert, and download the PEM result instantly. No account or software needed.
Is converting CER to PEM free?: Yes. It is free and unlimited for files up to 5 MB, with no account required. Larger files get 3 free conversions per day; beyond that, credit packs start at $1 and credits never expire.
Are my files stored or shared?: No. Files are processed in server memory and deleted immediately after conversion. Nothing is written to disk or retained.
Do I need to install anything?: No software installation needed. OmniConvert runs in the browser — just upload, convert, and download.

No account needed · Credits never expire · Share your token link across devices