What is a Template?
A Template securely stores Transloadit Assembly Instructions in a Workspace and is referenced in API requests through a template_id. It lets clients invoke a predefined processing workflow without sending its full instructions.
How Templates work
A Transloadit Template is a Workspace-managed workflow definition whose JSON describes named Assembly Steps, their parameters, and how outputs from earlier Steps flow into later ones. Referencing a stored definition avoids sending complete Instructions in each creation request, but does not make the workflow confidential: Assembly Status can expose template and merged_params. Properties supplied in params at request time, except allow_steps_override itself, are recursively merged over the loaded Template, subject to its Step override policy. That merge also enables runtime variation. Templates sit between application requests and Assembly execution, so their change management is part of the integration contract.
Key facts
- Step names form references within Assembly Instructions, so renaming a step can break downstream
userelationships even when every individual operation remains syntactically valid. - A
template_idselects stored instructions but does not by itself authenticate an API request; account authentication and any request-signing requirements remain separate controls. - Set
allow_steps_overridetofalsein the stored Template to reject requests that also supply Steps. Other request parameters can still override stored values. Require Signature Authentication for Auth Key requests and have a trusted back end sign only approved parameters; valid bearer tokens bypass that requirement and remain subject to their scopes and audience restrictions. Signatures cover serializedparams, not separate upload form fields. Those unsigned fields populate${fields.*}and override same-named signedfieldsvalues, so these controls alone do not secure dynamic inputs. Do not derive settings callers must not choose from those fields. - Templates created in a Workspace have no version pinning. To make a backward-incompatible change safely, create a new Template with its own
template_idand move callers over. Only Transloadit’s Builtin Templates are versioned by Transloadit.
When Templates matter
Use a Template to centralize workflow changes and avoid sending complete Assembly Instructions in each creation request. Set allow_steps_override to false to prevent Step overrides, and require Signature Authentication with trusted signing for Auth Key requests. These controls do not constrain unsigned upload fields or replace bearer-token scope restrictions, so review dynamic inputs separately. Updating a shared Template can affect every caller, so incompatible changes may require a new Template.