List subject line performance (coming soon)

GET

/api/v3/letters/subject-line-performances

const url = 'https://api.tryletterhead.com/api/v3/letters/subject-line-performances?api=true';
const options = {method: 'GET', headers: {Authorization: 'Bearer <token>'}};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}

curl --request GET \
  --url 'https://api.tryletterhead.com/api/v3/letters/subject-line-performances?api=true' \
  --header 'Authorization: Bearer <token>'

This endpoint returns the top 5 and bottom 5 performing subject lines for the authenticated company, ranked by open rate. As a v3 endpoint, it requires a company-derived API key.

It returns two arrays — top and bottom — each containing up to 5 items with the subject line text, open rate percentage, send count, and associated newsletters, channels, and organizations.

No analysis is included; this is purely metrics-driven.

Authorizations

bearerAuth

Parameters

Query Parameters

api

required

boolean

When set to true, this endpoint will accept authorization with your API Key.

Responses

200

Subject Line Performances (Coming Soon)

application/json

object

items

object

top

Array<object>

object

subject

string

openRate

integer

sent

integer

letter

string

channel

string

organization

string

bottom

Array<object>

object

subject

string

openRate

integer

sent

integer

letter

string

channel

string

organization

string

message

string

total

integer

Example

{
  "items": {
    "top": [
      {
        "subject": "Draft 720",
        "openRate": 100,
        "sent": 1,
        "letter": "vkky0g63zs",
        "channel": "black-bitter-iced-tea-times",
        "organization": "black-bitter-coffee-brand"
      },
      {
        "subject": "F1 Unlocked Template",
        "openRate": 100,
        "sent": 13,
        "letter": "nrhi21smx3",
        "channel": "black-bitter-coffee",
        "organization": "black-bitter-coffee-brand"
      },
      {
        "subject": "Harsh E2E Test",
        "openRate": 100,
        "sent": 1,
        "letter": "0xlfgg8owg",
        "channel": "black-bitter-coffee",
        "organization": "black-bitter-coffee-brand"
      },
      {
        "subject": "F1 Unlocked Template",
        "openRate": 92,
        "sent": 13,
        "letter": "ndefdg8zl0",
        "channel": "black-bitter-coffee",
        "organization": "black-bitter-coffee-brand"
      },
      {
        "subject": "F1 Unlocked Template",
        "openRate": 92,
        "sent": 13,
        "letter": "2tebekvmiu",
        "channel": "black-bitter-coffee",
        "organization": "black-bitter-coffee-brand"
      }
    ],
    "bottom": [
      {
        "subject": "Anna's Cupcake Shop",
        "openRate": 0,
        "sent": 0,
        "letter": "dtqw2gzyqu",
        "channel": "black-bitter-tea",
        "organization": "black-bitter-coffee-brand"
      },
      {
        "subject": "F1 Unlocked Template",
        "openRate": 0,
        "sent": 0,
        "letter": "17nsgad7m9",
        "channel": "black-bitter-coffee",
        "organization": "black-bitter-coffee-brand"
      },
      {
        "subject": "A New Right Quick",
        "openRate": 0,
        "sent": 3,
        "letter": "n3wdcbv4bs",
        "channel": "black-bitter-coffee",
        "organization": "black-bitter-coffee-brand"
      },
      {
        "subject": "Create and Monetize Great Newsletters Easily",
        "openRate": 0,
        "sent": 3,
        "letter": "4f3fsndi0s",
        "channel": "black-bitter-coffee",
        "organization": "black-bitter-coffee-brand"
      },
      {
        "subject": "F1 Unlocked Template",
        "openRate": 0,
        "sent": 0,
        "letter": "5gr5nkngrf",
        "channel": "black-bitter-coffee",
        "organization": "black-bitter-coffee-brand"
      }
    ]
  },
  "message": "Do something kind today",
  "total": 10
}

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