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Expression validation

The Cloudflare Filters API supports an endpoint for validating expressions.

OperationMethod + EndpointNotes
Validate expression via query string (?expression=) GET /filters/validate-exprAllows testing and validating expressions without changing anything
Validate expression via JSON objectPOST /filters/validate-exprAllows testing and validating expressions without changing anything

Examples

Validate expression via query string

Request

curl -X GET -H "X-Auth-Email: user@cloudflare.com" -H "X-Auth-Key: REDACTED" 'https://api.cloudflare.com/client/v4/filters/validate-expr?expression=ip.src==34'

Response

{
"result": null,
"success": false,
"errors": [
{
"message": "Filter parsing error:\n`ip.src==34`\n ^^ couldn't parse address in network: invalid IP address syntax\n"
}
],
"messages": null
}

Note the validation error in the response. In this example, the error is due to an invalid IP address format:

Filter parsing error:
`ip.src==34`
^^ couldn't parse address in network: invalid IP address syntax

Validate expression via JSON object

Request

curl -X POST \
-H "X-Auth-Email: user@cloudflare.com" \
-H "X-Auth-Key: REDACTED" \
-H "Content-Type: application/json" \
-d '{
"expression": "ip.src in {2400:cb00::/32 2405:8100::/2000 2405:b500::/32 2606:4700::/32 2803:f800::/32 2c0f:f248::/32 2a06:98c0::/29}"
}' "https://api.cloudflare.com/client/v4/filters/validate-expr"

Response

{
"result": null,
"success": false,
"errors": [
{
"message": "Filter parsing error:\n`ip.src in {2400:cb00::/32 2405:8100::/2000 2405:b500::/32 2606:4700::/32 2803:f800::/32 2c0f:f248::/32 2a06:98c0::/29}`\n ^^^^ number too large to fit in target type while parsing with radix 10\n"
}
],
"messages": null
}

Note the validation error in the response. In this example, the value for the subnet mask, /2000, is not a valid IPv6 CIDR mask:

Filter parsing error:
`ip.src in {2400:cb00::/32 2405:8100::/2000 2405:b500::/32 2606:4700::/32 2803:f800::/32 2c0f:f248::/32 2a06:98c0::/29}`
^^^^ number too large to fit in target type while parsing with radix 10