Your API key

Create one in the portal under API keys.

Browse the API

API reference

Signature templates

Create, edit and assign the signature templates your organisation uses.

8 endpoints

GET/api/v1/signatures

List templates

Every signature template in the organisation, default first.

signatures:read

This endpoint takes no parameters beyond the URL itself.

Example response

json

{
  "signatures": [
    {
      "id": "b8e0f1a2-3c4d-4e5f-8a9b-0c1d2e3f4a5b",
      "name": "Standard",
      "description": "The main company signature",
      "category": "general",
      "is_default": true,
      "version": 4,
      "updated_at": "2026-09-18T14:02:11.000Z"
    }
  ],
  "total": 6
}

Copy and paste

curl -X GET "https://api.usesigned.co.uk/api/v1/signatures" \
  -H "X-API-Key: $SIGNED_API_KEY"

Worth knowing

The list is paged when you pass page or limit. Without them you get the first 100.

POST/api/v1/signatures

Create a template

Creates a signature template. The HTML is compiled before it is saved, so a broken template is rejected rather than stored.

signatures:write

Parameters

JSON body

nameRequired
stringTemplate name.
up to 255 characters
example: "Standard"
descriptionOptional
stringWhat the template is for.
up to 2000 characters
html_contentRequired
stringHandlebars HTML. See the template variables in the guides.
example: "<table><tr><td><strong>{{display_name}}</strong></td></tr></table>"
text_contentOptional
stringPlain text version, used when the email client cannot show HTML.
categoryOptional
stringFree-text label for grouping templates.
default "general" · up to 50 characters
design_jsonOptional
stringSaved state of the visual designer. Ignored if you are not using the designer.
up to 200000 characters

Example request body

json

{
  "name": "Standard",
  "description": "The main company signature",
  "html_content": "<table><tr><td><strong>{{display_name}}</strong><br>{{job_title}}</td></tr></table>",
  "design_json": null
}

Example response

json

{
  "signature": {
    "id": "b8e0f1a2-3c4d-4e5f-8a9b-0c1d2e3f4a5b",
    "name": "Standard",
    "is_default": true,
    "version": 1,
    "created_at": "2026-09-25T10:15:00.000Z"
  }
}

Copy and paste

curl -X POST "https://api.usesigned.co.uk/api/v1/signatures" \
  -H "X-API-Key: $SIGNED_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name": "Standard","description": "The main company signature","html_content": "<table><tr><td><strong>{{display_name}}</strong><br>{{job_title}}</td></tr></table>","design_json": null}'

Worth knowing

The first template in an organisation becomes the default automatically.

GET/api/v1/signatures/{id}

Get a template

Returns one template including its HTML.

signatures:read

Parameters

In the path

idRequired
stringTemplate ID.
uuid

Example response

json

{
  "signature": {
    "id": "b8e0f1a2-3c4d-4e5f-8a9b-0c1d2e3f4a5b",
    "name": "Standard",
    "html_content": "<table><tr><td><strong>{{display_name}}</strong></td></tr></table>",
    "text_content": null,
    "category": "general",
    "is_default": true,
    "version": 4
  }
}

Copy and paste

curl -X GET "https://api.usesigned.co.uk/api/v1/signatures/{id}" \
  -H "X-API-Key: $SIGNED_API_KEY"

PATCH/api/v1/signatures/{id}

Update a template

Updates a template. Every save bumps the version, so a signature can always be traced back to a revision.

signatures:write

Parameters

In the path

idRequired
stringTemplate ID.
uuid

JSON body

nameOptional
stringTemplate name.
up to 255 characters
descriptionOptional
stringWhat the template is for.
up to 2000 characters
html_contentOptional
stringHandlebars HTML.
text_contentOptional
stringPlain text version.
categoryOptional
stringFree-text label for grouping templates.
up to 50 characters
design_jsonOptional
stringSaved state of the visual designer.
up to 200000 characters

Example request body

json

{
  "description": "The main company signature, updated September 2026"
}

Example response

json

{
  "signature": {
    "id": "b8e0f1a2-3c4d-4e5f-8a9b-0c1d2e3f4a5b",
    "version": 5
  }
}

Copy and paste

curl -X PATCH "https://api.usesigned.co.uk/api/v1/signatures/{id}" \
  -H "X-API-Key: $SIGNED_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"description": "The main company signature, updated September 2026"}'

DELETE/api/v1/signatures/{id}

Delete a template

Deletes a template. Refused if a rule still uses it, so signatures never silently fall back.

signatures:write

Parameters

In the path

idRequired
stringTemplate ID.
uuid

Example response

json

{
  "deleted": true
}

Copy and paste

curl -X DELETE "https://api.usesigned.co.uk/api/v1/signatures/{id}" \
  -H "X-API-Key: $SIGNED_API_KEY"

Worth knowing

If you delete the default template, the most recently updated template becomes the new default.

POST/api/v1/signatures/{id}/default

Make a template the default

Makes this template the one used by anyone no rule matches.

signatures:write

Parameters

In the path

idRequired
stringTemplate ID.
uuid

Example response

json

{
  "signature": {
    "id": "b8e0f1a2-3c4d-4e5f-8a9b-0c1d2e3f4a5b",
    "is_default": true
  }
}

Copy and paste

curl -X POST "https://api.usesigned.co.uk/api/v1/signatures/{id}/default" \
  -H "X-API-Key: $SIGNED_API_KEY"

POST/api/v1/signatures/{id}/duplicate

Duplicate a template

Copies a template, including its designer state, under the name "Copy of ...".

signatures:write

Parameters

In the path

idRequired
stringTemplate ID.
uuid

Example response

json

{
  "signature": {
    "id": "c9f1a2b3-4d5e-4f6a-9b0c-1d2e3f4a5b6c",
    "name": "Copy of Standard",
    "is_default": false
  }
}

Copy and paste

curl -X POST "https://api.usesigned.co.uk/api/v1/signatures/{id}/duplicate" \
  -H "X-API-Key: $SIGNED_API_KEY"

POST/api/v1/signatures/render

Render HTML

Renders Handlebars HTML with sample data without saving anything. Useful for previewing an edit before you commit it.

signatures:read

Parameters

JSON body

html_contentRequired
stringHandlebars HTML to compile.
dataOptional
objectValues to merge over the sample data. Same keys as the template variables.

Example request body

json

{
  "html_content": "<strong>{{display_name}}</strong>",
  "data": {
    "display_name": "Alex Morgan"
  }
}

Example response

json

{
  "html": "<strong>Alex Morgan</strong>",
  "data": {
    "display_name": "Alex Morgan",
    "job_title": "Operations Manager"
  }
}

Copy and paste

curl -X POST "https://api.usesigned.co.uk/api/v1/signatures/render" \
  -H "X-API-Key: $SIGNED_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"html_content": "<strong>{{display_name}}</strong>","data": {"display_name": "Alex Morgan"}}'