Custom Fingerprinting Rules

If our default grouping algorithm is separating occurrences that you would rather have combined or vice versa, then you can set up Custom Fingerprinting Rules.

To set your custom grouping rules, go to Project Settings -> [Your project] -> Custom Fingerprinting for the project you want to configure.

Here's an example configuration:

  {"condition": {"path": "body.trace.exception.class", "eq": "TimeoutError"},
    "fingerprint": "timeout-error",
    "title": "Timeout Error"
  {"condition": {"path": "body.trace.exception.class", "eq": "IndexError"},
    "fingerprint": "index-error"

The above configuration is a list of rules. Each rule is a JSON object that consists of a condition, a fingerprint, and an optional title.

Rules are applied in order, testing the condition against the incoming occurrence. If a match is found, the rule's fingerprint and title will be used instead of our default algorithm.

Occurrences with the same fingerprint are combined into an Item.

The title of the first occurrence of an Item is used as the title of the Item, and is only changed if the item is resolved and then later reactivated. Upon reactivation, the title of the reactivating occurrence is used as the new Item title.


The condition is defined as a single JSON object. It can either be:

  • a leaf condition, having a path key and an operator key (see list below).
  • a branch condition, having a single key named any, all, or none, whose value is a list of other conditions.

The path key describes a path from the root of the occurrence data to the data that the condition tests. Use dots (.) to select object properties or array elements. You can also use the * character in place of an array index or property name to select all matching elements; in this case, the condition will pass if the operator evaluates to true for any of the matching elements.


Here are a few commonly used paths:

body.trace.exception.classException class name
body.trace.exception.messageException message
body.trace.frames.0.filenameFilename of the first stack frame
body.trace.frames.-1.filenameFilename of the last stack frame
body.trace.frames.*.filenameFilename of any stack frame
body.trace.frames.*.methodMethod/function name of any stack frame
languageThe language name

You can use any value in your JSON payload as a path, including custom data. To view your JSON payloads, go into an occurrence and click on View JSON at the bottom of the screen.

Here's a simple example of some error JSON:

  "body": {
    "trace": {
      "frames": [
          "method": "HTMLDocument.e._wrapped",
          "lineno": 32,
          "colno": 100,
          "filename": ""
      "exception": {
        "message": "Boomerang is not defined",
        "class": "ReferenceError",
        "description": "Error while initializing Heroku header"
  "server": {
    "host": "web01"

In this example, the value of body.trace.frames.0.lineno is 32, and the value of is web01.


The following operators are available:

neqNot Equals
inContained in the string or list
ninNot contained in the string or list
containsContains the string, element, or key (case sensitive)
icontainsContains the string, element, or key (case insensitive)
ncontainsDoes not contain the string, element, or key (or is not a string, array, or object)
startswithStarts with the string
endswithEnds with the string
gtGreater than
gteGreater than or equal to
ltLess than
lteLess than or equal to
regex_matchRegular expression matcher

For the numeric operators (gt, gte, lt, lte): the right side must be a number, and the left side (data from the occurrence) will be coerced to a number, defaulting to 0.

Example: Match items whose exception class is NameError

  "path": "body.trace.exception.class",
  "eq": "NameError"

Example: Match items whose exception class is TypeError or ValueError, and exception message contains the string "database"

  "all": [
    { "any": [
      { "path": "body.trace.exception.class", "eq": "TypeError" },
      { "path": "body.trace.exception.class", "eq": "ValueError" }
    { "path": "body.trace.exception.message", "contains": "database" }

Note: If your exception has nested stack traces, rather than using body.trace.exception.message, you'll need to use body.trace_chain.0.exception.message, and so on for any paths that begin with body.trace.

Example: Match items whose message body is 7 to 10 digits and does not begin with 4321

  "all": [
    {"path": "body.message.body", "regex_match": "^(?!4321).*"},
    {"path": "body.message.body", "regex_match": "^\\d{7,10}$"}


Occurrences with the same fingerprint are combined into an Item. To add occurences to an existing group item created by manual merging, use the fingerprint group-item-###, e.g. group-item-123. See the merging guide for an example.


The title is an optional text description that is displayed when viewing an item. It must be a string, of length 1-255 characters. You can change the title in this configuration without impacting the fingerprint. The new title will take effect if the item is reactivated after being resolved.


Both fingerprint and title can contain template markers (wrapped in {{double braces}}) as well as hardcoded strings.

There are two special markers:

  • {{default_fingerprint}}: will be replaced with the fingerprint hash calculated by our default algorithm.
  • {{default_title}}: will be replaced with the title calculated by our default algorithm.

These can be used to tune the fingerprinting algorithm without entirely replacing it.

Additionally, any part of the occurrence JSON body may be referenced by path. For example

  • {{ body.trace.exception.class }} will be replaced with the exception class.
  • {{ body.trace.exception.message }} will be replaced with the exception message.

You can combine this with static text or the special markers achieve many kinds of fingerprinting.

Complete Example

Here's an example complete configuration with three rules.

    "condition": {
      "path": "body.trace.exception.class",
      "in": ["EOFError", "Errno::ECONNREFUSED", "Errno::ETIMEDOUT"]
    "fingerprint": "connection-error",
    "title": "Connection error"
    "condition": {"all": [
      {"path": "body.trace.exception.class", "eq": "TimeoutError"},
      {"path": "body.trace.frames.*.filename", "contains": "payments"}
    "fingerprint": "payments-timeout-error",
    "title": "Timeout error in payments code"
    "condition": {
      "path": "body.trace.exception.class",
      "eq": "ActionController::RoutingError"
    "fingerprint": "{{ default_fingerprint }}-{{ context }}",
    "title": "{{default_title }} in {{ context }}"


If you are explicitly sending a fingerprint in an occurrence's payload and you have custom grouping rules, the custom grouping rule will not override the explicitly set fingerprint by default.

You can override this default behavior for a Project by checking the 'Ignore Client-side fingerprinting' check box on the Custom Fingerprinting page of the Project settings.