# Customer.io Email testing API

**Canonical:** https://apis.io/apis/customer-io/customer-io-email-testing-api/  
**Provider:** Customer.io — https://apis.io/providers/customer-io/  
**Base URL:** https://track.customer.io  
**Documentation:** https://docs.customer.io/integrations/api/track/

Customer.io Email testing API is one of 48 APIs that [Customer.io](https://apis.io/providers/customer-io/) publishes on the [APIs.io](https://apis.io/) network, described by a machine-readable OpenAPI specification. This API exposes 6 JSON Schema definitions. Tagged areas include Email testing. The published artifact set on APIs.io includes an OpenAPI specification, API documentation, and 6 JSON Schemas.

Check an email before you publish or send it. - [Render](/integrations/api/design-studio/tag/email-testing/renderEmail/) returns the compiled HTML with liquid left intact. - [Preview](/integrations/api/design-studio/tag/email-testing/previewEmail/) evaluates liquid against a real profile or sample data. - [Review](/integrations/api/design-studio/tag/email-testing/reviewEmail/) reports issues that could stop the email from sending or breach compliance standards. - [Test send](/integrations/api/design-studio/tag/email-testing/testSendEmail/) delivers the email to addresses you choose. - **Inbox previews** render the email in real email clients. [Submit a job](/integrations/api/design-studio/tag/email-testing/submitInboxPreview/), poll it, then fetch each capture. Inbox previews use credits; check your balance and the available clients with the account-level endpoints in this section.

## Operations (10)

| Method | Path | Summary |
|---|---|---|
| GET | `/v1/design_studio/emails/{id}/render` | Render an email |
| POST | `/v1/design_studio/emails/{id}/preview` | Preview an email |
| POST | `/v1/design_studio/emails/{id}/test_send` | Send a test email |
| GET | `/v1/design_studio/emails/{id}/review` | Review an email |
| GET | `/v1/design_studio/inbox_previews/clients` | List inbox preview options |
| GET | `/v1/design_studio/inbox_previews/credits` | Get preview credit balance |
| POST | `/v1/design_studio/emails/{id}/inbox_previews` | Send for inbox previews |
| GET | `/v1/design_studio/emails/{id}/inbox_previews/{run_id}` | Get an inbox preview job |
| GET | `/v1/design_studio/emails/{id}/inbox_previews/{run_id}/captures/{client_id}` | Get a preview screenshot |
| GET | `/v1/design_studio/inbox_previews/jobs` | List inbox preview history |

## Machine-readable artifacts (10)

- **OpenAPI** — https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/openapi/customer-io-email-testing-api-openapi.yml
- **Documentation** — https://docs.customer.io/integrations/api/app/
- **Documentation** — https://docs.customer.io/integrations/data-in/connections/http-api/
- **Documentation** — https://docs.customer.io/integrations/api/customerio-apis/
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/json-schema/customer-io-campaign-object-schema.json
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/json-schema/customer-io-transformers-schema.json
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/json-schema/customer-io-campaign-request-schema.json
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/json-schema/customer-io-newsletter-object-schema.json
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/json-schema/customer-io-activity-object-schema.json
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/json-schema/customer-io-anonymous-events-request-schema.json

## Other Customer.io APIs (12)

- [Customer.io Track API](https://apis.io/apis/customer-io/track-api/)
- [Customer.io Activities API](https://apis.io/apis/customer-io/customer-io-activities-api/)
- [Customer.io Alias API](https://apis.io/apis/customer-io/customer-io-alias-api/)
- [Customer.io Batch API](https://apis.io/apis/customer-io/customer-io-batch-api/)
- [Customer.io Broadcasts API](https://apis.io/apis/customer-io/customer-io-broadcasts-api/)
- [Customer.io Collections API](https://apis.io/apis/customer-io/customer-io-collections-api/)
- [Customer.io Customers API](https://apis.io/apis/customer-io/customer-io-customers-api/)
- [Customer.io Exports API](https://apis.io/apis/customer-io/customer-io-exports-api/)
- [Customer.io Group API](https://apis.io/apis/customer-io/customer-io-group-api/)
- [Customer.io Identify API](https://apis.io/apis/customer-io/customer-io-identify-api/)
- [Customer.io Messages API](https://apis.io/apis/customer-io/customer-io-messages-api/)
- [Customer.io Newsletters API](https://apis.io/apis/customer-io/customer-io-newsletters-api/)

## Tags

Email testing

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/apis/customer-io/customer-io-email-testing-api/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/customer-io/.