A Certificate Authority (CA) bundle is a file that contains the following details about the SSL certificate:
- Who issued it.
- Any certificates of the authority that issued it.
- The “chain of trust” for the issuer. Note: A certificate authority can vouch for other certificate authorities, which results in a “chain of trust.” In order for a certificate authority to sell certificates, another certificate authority must vouch for them.
- Certificate revocation lists (CRLs).
Web browsers have a built-in list of trusted certificate authorities, and they use the list to determine whether to trust an authority.