Build API

Learn about using the build API to test sites from client-side IDEs.

Stacklane provides a build API for syncing files, validating + building sites, and generating shareable test domains. To see this API in action view the source code for the WebStorm plugin.


The build API supports a reasonable number of anonymous users per day. To indicate anonymous authentication pass Bearer anonymous in the Authorization header. Only anonymous users are currently supported.

Endpoint and Project IDs

All API verbs are performed at the following endpoint:{ProjectId}

{ProjectId} should be a GUID-like string between 20 and 64 characters (a-z A-Z 0-9 - _). This could be a randomly generated value or SHA-256 hex value. For anonymous users the client code should take care to produce sufficiently unique values to prevent collisions. Generally this would be a unique value produced at IDE startup. To perform efficient PATCH operations (syncing), this unique GUID-like value should not frequently change.


Produces a JSON response with the current contents of the ProjectId. If the ProjectId does not exist the response status is 404.

JSON Response

    { "path": "/🎛.yaml", "md5": "m1ChXoeAKCZirpWm3sbPAg==" }


PUT completely replaces all files for the site. It receives the request Content-Type of application/zip. The body should contain the binary zip data.

PUT always creates a newProjectId if one does not exist, therefore unlike other verbs it will never return 404. The response from a successful upload is the current contents as defined by GET.


Use PATCH for incremental syncing of an existing ProjectId. When a ProjectId already exists this is the quickest way to generate a new test instance. If the ProjectId does not exist the response status is 404. This would typically be transparent to the user — for example, if GET returns 404, then automatically perform a PUT instead of trying a PATCH. PATCH takes two forms depending on the request Content-Type.

Add/Replace Files (application/zip)

Similar to PUT, but the zip should only contain the files to create or update. No files will be deleted in this operation. Use the md5 from GET to determine what files need to be updated.

Prune/Delete Files (application/json)

Use this operation if, based on the current contents (GET), it is determined that certain files should be deleted. This operation informs the server what files to keep / retain. Any other files not specified will be deleted.



Use the POST operation on a previously uploaded/synced ProjectId. This step performs the validation and build of the files, reports any errors, and if successful returns a unique domain name for testing and sharing.

Passing Credentials

The POST operation may optionally pass development credentials. When passing the credential JSON file to the build process, specify a Content-Type of application/json and the JSON credentials file as the content/payload of the request.

Plain Text Response

Pass text/plain in the Accept header to receive simple build messages, one per line. In a successful build with no errors, the final line will start with https:// and contain the unique test domain for that build.

JSON Response

A more information rich option is to pass application/json in the Accept header. This allows grouping of entries, and output of source code snippets which may have compilation errors.

The overall format of a JSON response is one JSON document per newline.

Every per-line JSON document will have a type property which may be one of:

  • debug
  • info
  • warn
  • error
  • group-begin
  • group-end
  • result

In addition to type, nearly every entry will have a human readable message property.

Each entry may or may not belong to a group. This is an example of an error occurring within a group:

{"type":"group-begin", "group":{"name":"Endpoints","id":"grp-12"}}
{"type":"error", "file":"/GET.js", "group":{"name":"Endpoints","id":"grp-12"}, /*....*/ }
{"type":"group-end", "group":{"name":"Endpoints","id":"grp-12"}}

The final entry in a successful build will have a type of result and a url property:


Certain entries may contain a file property, especially for compilation errors. The file property contains an absolute path to a file within the source code. When this property is present, there are other optional pieces of information which may be included when available. The following example has newlines added only for readability (newlines are never output within an entry):

  "message":"Type Mismatch: expected (string=\"x\"), was number",
  "source":{"offset":5,"type":"js","value":"}\nlet v = 'x';\nv = 5;\n({});\n"}

Both line and source are optional. The source.offset refers to the starting point for the source.value. Therefore in this example source.value starts on line 6, and includes lines 7, 8 (the line where the error is), 9, and 10.