--- schema_version: "1" id: 0c4b28eebe7c5d690e0c597c2e67ccb6e09064fbc59da6adf89c0afcf10f96d6 title: Use Named Credential Formula Functions in Custom Headers collection: admin version: current locale: en-us portal_url: https://docs.salesforce.com/admin/current/en-us/xcloud/264-0-0/nc_named_creds_formula_functions.md canonical_url: https://help.salesforce.com/s/articleView?id=xcloud.nc_named_creds_formula_functions.htm&release=264.0.0&type=5 source_site: help.salesforce.com content_type: documentation content_hash: 435a430bfb2c5939048393aa24607e0e8f5109de0b0f2f831ee2631094c6ee6c description: Formula functions can be used in the value field of a custom header of a named credential or external credential. products: - Security release: "264" --- # Use Named Credential Formula Functions in Custom Headers Formula functions can be used in the value field of a custom header of a named credential or external credential. ### Required Editions
Available in: both Salesforce Classic (not available in all orgs) and Lightning Experience
Available in: all editions
![Note](https://sf-zdocs-cdn-prod.zoominsoftware.com/tdta-xcloud-security-264-0-0-production-enus/8cecd769-ab2d-4e07-addf-c4f2927925e1/images/icon_note.png) Note Not all Salesforce formula functions are supported for named and external credential custom headers. We recommend using these formula functions for authentication use cases. A binary large object (BLOB) is a collection of binary data stored as a single entity. For named credentials, BLOBs can store binary executable code used in custom header formulas. See [Create and Edit Custom Headers](https://help.salesforce.com/s/articleView?id=xcloud.nc_create_custom_headers.htm&release=264.0.0&type=5 "Use custom headers to make unique secure connections to external data sources."). Formula fields can contain up to 3,900 characters, including spaces, return characters, and comments. If your formula requires more characters, create separate formula fields and reference them in another formula field. The maximum number of displayed characters after an evaluation of a formula expression is 1,300, which can truncate access tokens in custom headers. Formula Functions for Named Credentials | Function | Description | | --- | --- | | BASE64DECODE(expr) | Input String Output BlobValue Description Decode the Base64-encoded String expression to a binary. | | BASE64ENCODE(expr) | Input BlobValue Output String Description Encode the binary BLOB expression as a Base64-encoded String. | | BLOB(expr) | Input String Output BlobValue Description Convert the value to a UTF-8 binary BLOB. | | HASH(algorithm, expr) | Input String, BlobValue Output BlobValue Description Given a binary value to hash, use algorithm to get the binary hash. The only supported hashing algorithm is SHA-256. | | HEX(expr) | Input BlobValue Output String Description Represents the given BLOB expression as a base-16 lower-case encoded String. This hex encoding contains the binary data expected by encryption functions. | | HMAC(algorithm, valueToSign, secretSigningKey) | Input String, BlobValue, BlobValue Output BlobValue Description Use algorithm to sign the given binary valueToSign with a binary secret signing key. The resulting message authentication code is a binary value. The only supported algorithm is SHA-256. | | SIGN(algorithmName, input, privateKey) | Input String, BlobValue, BlobValue Output BlobValue Description Compute a unique digital signature for the input string using the specified algorithm and private key. Supported algorithms are RSA, RSA-SHA1, RSA-SHA256, RSA-SHA384, RSA-SHA512, ECDSA-SHA256, ECDSA-SHA256-PLAIN, ECDSA-SHA384, and ECDSA-SHA512. | | SIGN\_WITH\_CERTIFICATE(algorithmName, input, certDevName) | Input String, BlobValue, String Output BlobValue Description Compute a unique digital signature for the input string using the specified algorithm and the unique name of a certificate in the Salesforce org. Supported algorithms are RSA, RSA-SHA1, RSA-SHA256, RSA-SHA384, RSA-SHA512, ECDSA-SHA256, ECDSA-SHA256-PLAIN, ECDSA-SHA384, and ECDSA-SHA512. | ## Examples - This example shows encoding a username and password stored in an external credential. The `BLOB` function first converts a string of form username:password into a binary. `BASE64ENCODE` then converts the binary into an encoded string. `myExternalCredential` is the name of an external credential. ``` BASE64ENCODE(BLOB($Credential.myExternalCredential.Username & ':' & $Credential.myExternalCredential.Password)) ``` - This example sets a header named `X-Username` with a base-16, SHA-256-hashed username as the value. `req` is an `HTTPRequest`. `Username` is an authentication parameter attached to a principal. ``` req.setHeader('X-Username', '{!HEX(HASH(\'SHA-256\', BLOB($Credential.myExternalCredential.Username)))}'); ``` - This example sets the `X-Body` header as the base-16, hashed _evaluated_ body, meaning that all formulas within the request body are evaluated. `BLOB` isn’t required here because `$Credential.myExternalCredential.Body` is returned as a BLOB type rather than as a String. ``` req.setHeader('X-Body', '{!HEX(HASH(\'SHA-256\', $Credential.myExternalCredential.Body))}'); ``` #### See Also - [Use Custom Headers for Basic Authentication with Named Credentials](https://help.salesforce.com/s/articleView?id=xcloud.nc_custom_headers_basic_auth.htm&release=264.0.0&type=5 "Create an external credential with a custom header that uses HTTP Basic authentication.") - [Formula Operators and Functions by Context](https://help.salesforce.com/s/articleView?id=platform.customize_functions.htm&type=5&language=en_US) - [Calculate Field Values With Formulas](https://help.salesforce.com/s/articleView?id=platform.customize_formuladef.htm&type=5&language=en_US) - [_Apex Developer Guide_: Merge Fields for Apex Callouts That Use Named Credentials](https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_callouts_named_credentials_merge_fields.htm)