[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"howto:der:windows:en":3},{"resolvedFromAlias":4,"canonicalExt":5,"ext":5,"name":6,"category":7,"categoryName":8,"updatedAt":9,"os":10,"osLabel":11,"quickSolution":12,"stepByStep":13,"recommendedSoftware":16,"alternativeMethods":17,"commonIssues":18,"securityNote":37,"extensionPath":38,"extensionLabel":39,"breadcrumbs":40,"metaDescription":50},false,"der","DER-encoded X.509 Certificate","certificates","Certificates","2026-06-12T09:18:40.304Z","windows","Windows","To open .DER files on Windows, install OpenSSL (from a trusted source used in your environment).",[14,15],"Install OpenSSL (from a trusted source used in your environment).","Open Command Prompt or PowerShell and run: openssl x509 -in yourcert.der -inform DER -text -noout",[],[],[19,25,31],{"title":20,"description":21,"steps":22},"OpenSSL says it cannot read the certificate (wrong format)","This often happens when the file is PEM (Base64 text) but you told the tool it is DER, or when the file is not an X.509 certificate at all.",[23,24],"Try reading it as DER explicitly: openssl x509 -in file.der -inform DER -text -noout","If that fails and the file looks like text with BEGIN/END lines, try PEM: openssl x509 -in file.der -inform PEM -text -noout",{"title":26,"description":27,"steps":28},"The system/app expects PEM but you only have DER","Many configurations and libraries accept PEM text files, while .der is binary. PEM is Base64-encoded DER, so you can convert between them.",[29,30],"Convert DER to PEM: openssl x509 -in cert.der -inform DER -out cert.pem -outform PEM","Use the resulting .pem file where the software expects PEM",{"title":32,"description":33,"steps":34},"File extension confusion (.der vs .cer) and certificate import problems","Some environments treat .cer as either DER or PEM depending on content, while .der strongly implies binary DER. Import failures often come from using the wrong encoding for the import tool.",[35,36],"Inspect the file with OpenSSL using the correct input type (DER vs PEM) to confirm what it contains","If needed, convert to PEM or keep as DER depending on what the target importer expects",".der certificate files typically contain public certificate data, not executable content, but they can still be used in trust decisions; only install/import certificates from sources you trust.","/file-extension/der",".DER",[41,44,47],{"label":42,"to":43},"Home","/",{"label":45,"to":46},"How To","/file-extension",{"label":48,"to":49},"Open .DER on Windows","/how-to/open-der-on-windows","Learn how to open .DER files on Windows with step-by-step instructions, recommended software, and troubleshooting tips."]