> ## Documentation Index > Fetch the complete documentation index at: https://docs.helohq.com/llms.txt > Use this file to discover all available pages before exploring further. # Update a template > Modifies an existing template. Only the provided fields are changed. ## OpenAPI ````yaml /openapi.json patch /templates/{id} openapi: 3.1.0 info: description: Helo Email API (https://helohq.com) version: 1.0.0 title: Helo API servers: - url: https://api.helohq.com security: [] tags: - name: Activity description: >- Track and retrieve message activity, including messages, delivery and engagement events. - name: Broadcasts description: Manage and track broadcast email campaigns. - name: Channels description: Create and manage communication channels for organizing messages. - name: Domains description: Register, verify, and manage domains for email sending. - name: Sending description: Send transactional and broadcast emails. - name: Statistics description: Access activity statistics. - name: Templates description: Manage templates for sending. - name: Webhooks description: Create and manage webhooks for event notifications. paths: /templates/{id}: patch: tags: - Templates summary: Update a template description: Modifies an existing template. Only the provided fields are changed. operationId: Templates_update parameters: - name: id in: path required: true schema: type: string format: uuid requestBody: content: application/json: schema: $ref: '#/components/schemas/UpdateTemplateRequest' required: true responses: '200': description: OK content: application/json: schema: $ref: '#/components/schemas/TemplateResponse' '401': $ref: '#/components/responses/401' '403': $ref: '#/components/responses/403' '404': $ref: '#/components/responses/404' '409': $ref: '#/components/responses/409' '422': $ref: '#/components/responses/422' '500': $ref: '#/components/responses/500' security: - bearerAuth: [] x-codeSamples: - lang: ruby source: |- Helo.configure do |config| config.api_key = ENV.fetch("HELO_API_KEY") end id = "550e8400-e29b-41d4-a716-446655440000" update_template_request = Helo::UpdateTemplateRequest.new( name: "test-name", subject: "test-subject", html: "test-html", mjml: "test-mjml", text: "test-text", channel_ids: ["550e8400-e29b-41d4-a716-446655440000", "6ba7b810-9dad-11d1-80b4-00c04fd430c8"], version: 123 ) Helo::Templates.update(id, update_template_request) - lang: javascript source: |- import Helo from "@helo-email/sdk"; const apiKey = process.env.HELO_API_KEY; const helo = new Helo(apiKey); const result = await helo.templates.update( "550e8400-e29b-41d4-a716-446655440000", { name: "test-name", subject: "test-subject", html: "test-html", mjml: "test-mjml", text: "test-text", channelIds: ["550e8400-e29b-41d4-a716-446655440000"], version: 123, }, ); - lang: go source: "package main\n\nimport (\n\t\"context\"\n\t\"log\"\n\t\"os\"\n\n\t\"github.com/helo-email/helo-sdk-go\"\n)\n\nfunc main() {\n\tclient := helo.NewHelo(os.Getenv(\"HELO_API_KEY\"))\n\tctx := context.Background()\n\n\tparams := &helo.UpdateTemplateRequest{\n\t\tName: \"test-name\",\n\t\tSubject: \"test-subject\",\n\t\tHtml: \"test-html\",\n\t\tMjml: \"test-mjml\",\n\t\tText: \"test-text\",\n\t\tChannelIds: []string{\"550e8400-e29b-41d4-a716-446655440000\"},\n\t\tVersion: 123,\n\t}\n\tresult, err := client.Templates.Update(ctx, \"550e8400-e29b-41d4-a716-446655440000\", params)\n\tif err != nil {\n\t\tlog.Fatal(err)\n\t}\n\t_ = result\n}" - lang: csharp source: >- using HeloEmail.Sdk.Templates; var template = await helo.Templates.Update("550e8400-e29b-41d4-a716-446655440000", new UpdateTemplateRequest { Name = "test-name", Subject = "test-subject", Html = "test-html", Mjml = "test-mjml", Text = "test-text", ChannelIds = ["550e8400-e29b-41d4-a716-446655440000"], Version = 10, }); - lang: python source: |- import sdk_helo_email as helo client = helo.Helo() # reads HELO_API_KEY from the environment template = client.templates.update( "550e8400-e29b-41d4-a716-446655440000", name="test-name", subject="test-subject", html="test-html", mjml="test-mjml", text="test-text", channel_ids=["550e8400-e29b-41d4-a716-446655440000"], version=10, ) components: schemas: UpdateTemplateRequest: type: object properties: name: type: string description: Renames the template. Cannot be cleared. Maximum 64 characters. subject: type: string description: Cannot be cleared. Maximum 256 characters. html: type: - string - 'null' description: > Replaces the html, and clears any stored mjml (switching the template back to plain HTML authoring). Set to null to remove the html - blank values are rejected. Maximum 500,000 characters. mjml: type: - string - 'null' description: > Replaces the mjml source, recompiling the html from it. Set to null to remove the mjml source while keeping the html already compiled from it - blank values are rejected. Maximum 500,000 characters, and the compiled html must also be within the html limit. text: type: - string - 'null' description: > Replaces the plain text content. Set to null to remove it - blank values are rejected. Maximum 100,000 characters. channelIds: type: - array - 'null' items: type: string format: uuid description: > Replaces the channels the template is scoped to. Set to null or an empty array to remove channel scoping, making the template available to every channel in the account. version: type: integer format: int64 description: > The version of the template the update was based on, as returned by a previous read. If the template has since been modified the update is rejected with 409 Conflict, so concurrent edits aren't silently overwritten. description: > Only provided fields are changed - an omitted field leaves the existing value unchanged. Supplying both html and mjml in the same request is rejected, as is an update that would leave the template with no html or text content. Supply version to make the update conditional - without it, the last write wins. TemplateResponse: type: object properties: id: type: string format: uuid createdAt: type: string format: date-time updatedAt: type: string format: date-time version: type: integer format: int64 description: > Opaque version, changing on every update. Pass it back as the version of an update to have the update rejected if the template has been modified in the meantime. name: type: string subject: type: string html: type: string mjml: type: string text: type: string channelIds: type: array items: type: string format: uuid required: - id - createdAt - updatedAt - version - name - subject ErrorResponse: description: Standard error response body. type: object properties: type: description: A URI reference identifying the problem type. type: string title: description: Short, human-readable summary of the problem. type: string instance: description: URI reference identifying the specific occurrence of the problem. type: string status: description: HTTP status code. type: integer format: int32 code: description: Application-specific error code. type: string detail: description: Human-readable explanation of this specific occurrence. type: string requestId: description: Unique request ID, useful for support correlation. type: string errors: description: Field-level validation errors, keyed by field name. type: object additionalProperties: type: array items: $ref: '#/components/schemas/ValidationError' ValidationError: description: A single field validation error. required: - message type: object properties: message: description: Description of the validation failure. type: string responses: '401': description: Unauthorized content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '403': description: Forbidden content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '404': description: Not Found content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '409': description: > Conflict - the template has been modified since the version supplied in the request. Fetch the template and retry. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '422': description: Validation Failed content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '500': description: Internal Server Error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.