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Uptime Check

Synthetics is in beta for the Datadog US Site. To request access, complete the Datadog Synthetics request form.


Uptime Checks are HTTP requests (GET, POST, PUT, etc.) executed by Datadog to your web properties or application endpoints at configurable periodic intervals from multiple locations around the world. These checks verify that your applications are responding to requests, as well as that they meet any conditions you define—such as response time, HTTP status code, and header or body contents.



Define the request you want to be executed by Datadog:

Uptime Check make request
  1. Choose the Method and URL to query. Available Methods are:

    • GET
    • POST
    • PATCH
    • PUT
    • DELETE
  2. Optionally, click on Advanced options to enrich your request with custom request headers, authentication credentials, body content, or cookies.

  3. Name your Uptime Check.

  4. Optionally, add tags to filter your Uptime Check in the Synthetics page.

  5. Pick locations to run the test from. Available locations are:

    • Frankfurt (Request made from an AWS Datacenter)
    • Tokyo (Request made from an AWS Datacenter)
  6. Choose a Check frequency between “1 run per minute” and “1 run per week”.

  7. Finish by clicking on Test URL to try out the request configuration. You should see a response preview show up in the right side of your screen.


When running an Uptime Check, you must define at least one assertion that should be monitored by Datadog. An assertion is defined by a parameter, a comparator, and a value.

Parameter Comparators Value type
Status Code is, is not Integer
Response time less than Integer
Headers contains, is, is not, matches for contains/is/is not: String
for matches: RegexStrings
Body contains, is, is not, matches for contains/is/is not: String
for matches: RegexStrings

If you define an assertion on the content of Headers, you must define the headers name and the associated value.

Click on Add new assertion to add up to 10 assertions for your Uptime Check.

Note: If you clicked on Test URL, then the basic assertions are automatically filled:


Use the Test URL response to quickly add status code, response time or headers from the test response as one of the Uptime Check assertions:



A notification is sent if at least one of the assertion fails. To configure notifications:

  1. Select users and/or services to send the notifications to. Note that you can use the @-notification feature in the message field.
  2. Enter a message for the Uptime Check. This field allows standard Markdown formatting. Notification messages include the message defined in this section and information about which assertion failed and why.
  3. Click Save to save your Uptime Check.

Notifications example:


Network timings

The Synthetics details page displays the following network timings:

Timing Description
DNS Time spent resolving the DNS name of the last request.
Connect Time spent establishing a connection to the server.
SSL Time spent for the TLS handshake. If the last request is not over HTTPS, this metric does not appear.
TTFB (time to first byte) Time spent waiting for the first byte of response to be received.
Download Time spent downloading the response.

Response time is the sum of these network timings.


A check is considered FAILED if it doesn’t satisfy the assertions configured for this check, or if the request failed for another reason. These reasons include:

Error Description
CONNRESET The connection was abruptly closed by the remote server. Possible causes include the webserver encountering an error or crashing while responding, loss of connectivity of the webserver, etc.
DNS DNS entry not found for the check URL. Possible causes include misconfigured check URL, wrong configuration of your DNS entries, etc.
INVALID_REQUEST The configuration of the check is invalid (e.g., typo in the URL).
SSL The SSL connection couldn’t be performed; see below for more detailed explanations.
TIMEOUT The request couldn’t be completed in a reasonable time.

SSL errors

Error Description
CERT_CHAIN_TOO_LONG The certificate chain length is greater than the supplied maximum depth.
CERT_HAS_EXPIRED The certificate is expired.
CERT_NOT_YET_VALID The certificate is not valid until a future date.
CERT_REJECTED The root CA is marked to reject the purpose specified.
CERT_REVOKED The certificate was revoked by the issuer.
CERT_UNTRUSTED The root CA is not marked as trusted for its intended purpose.
CERT_SIGNATURE_FAILURE The signature of the certificate is not valid.
CRL_HAS_EXPIRED The certificate revocation list (CRL) has expired.
CRL_NOT_YET_VALID The certificate revocation list (CRL) is not valid until a future date.
CRL_SIGNATURE_FAILURE The CRL signature of the certificate is not valid.
DEPTH_ZERO_SELF_SIGNED_CERT The passed certificate is self-signed and the same certificate cannot be found in the list of trusted certificates.
ERROR_IN_CERT_NOT_AFTER_FIELD There is a format error in the notAfter field in the certificate.
ERROR_IN_CERT_NOT_BEFORE_FIELD There is a format error in the notBefore field in the certificate.
ERROR_IN_CRL_LAST_UPDATE_FIELD The CRL lastUpdate field contains an invalid time.
ERROR_IN_CRL_NEXT_UPDATE_FIELD The CRL nextUpdate field contains an invalid time.
INVALID_CA A CA certificate is not valid because it is not a CA or its extensions are not consistent with the intended purpose.
INVALID_PURPOSE The certificate that was provided cannot be used for its intended purpose.
OUT_OF_MEM An error occurred while allocating memory.
PATH_LENGTH_EXCEEDED The basicConstraints pathlength parameter was exceeded.
SELF_SIGNED_CERT_IN_CHAIN A self-signed certificate exists in the certificate chain. The certificate chain can be built using the untrusted certificates, but the root CA cannot be found locally.
UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY The public key in the certificate cannot be read.
UNABLE_TO_DECRYPT_CERT_SIGNATURE Unable to decrypt the signature of the certificate.
UNABLE_TO_DECRYPT_CRL_SIGNATURE The CRL signature cannot be decrypted. (The actual signature value cannot be determined.)
UNABLE_TO_GET_CRL The certificate revocation list (CRL) is not found.
UNABLE_TO_GET_ISSUER_CERT Unable to find the certificate for one of the certificate authorities (CAs) in the signing hierarchy, and that CA is not trusted by the local application.
UNABLE_TO_GET_ISSUER_CERT_LOCALLY The issuer certificate of a locally found certificate is not found. This usually means that the list of trusted certificates is not complete.
UNABLE_TO_VERIFY_LEAF_SIGNATURE No signatures are verified because the certificate chain contains only one certificate, which is not self-signed, and the issuer is not trusted.

Further Reading