# Import contacts (CSV)

> POST /audiences/:audience_id/contacts/import — bulk-import contacts from a CSV.

`POST /audiences/:audience_id/contacts/import`

Import up to **10,000 contacts** (max **5 MB**) from a CSV. The CSV can be sent as a JSON body field or as a raw `text/csv` / `text/plain` body. A header row is optional — if present, column names are matched to contact fields (`email`, `first_name`, `last_name`, `unsubscribed`). By default, any other columns are **automatically registered as custom properties** (so `company`, `plan`, … survive and become `{{merge}}` tags). Pass `create_properties: false` for strict mode, where only columns matching an already-registered property are kept and the rest are reported in `ignored_columns`.

**Body**

| Name | Type | Required | Description |
| --- | --- | --- | --- |
| `csv` | string | Yes | CSV text. The `email` column is always required. Other columns map to contact fields or custom properties. You can also `POST` a raw `text/csv` body instead of a JSON wrapper. |
| `on_conflict` | string | No | `upsert` (default) — update the existing contact when the email already exists. `skip` — leave it untouched. Can also be passed as a query parameter `?on_conflict=skip` when using a raw CSV body. |
| `create_properties` | boolean | No | Defaults to `true` — non-builtin CSV columns are auto-registered as string custom properties (up to 50 new per import) so no data is silently dropped. Set to `false` (or `?create_properties=false`) to keep only already-registered columns. |

**Node.js**

```js
import { MailBlastr } from 'mailblastr';

const mb = new MailBlastr('mb_xxxxxxxxx');

const { data, error } = await mb.contacts.import({
  audienceId: 'AUDIENCE_ID',
  "csv": "email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace"
});
console.log({ data, error });
```

**Ruby**

```ruby
require 'net/http'
require 'uri'

uri = URI('https://api.mailblastr.com/audiences/AUDIENCE_ID/contacts/import')
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = true
req = Net::HTTP::Post.new(uri)
req['Authorization'] = 'Bearer mb_xxxxxxxxx'
req['Content-Type'] = 'application/json'
req.body = <<~JSON
{
  "csv": "email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace"
}
JSON
res = http.request(req)
puts res.body
```

**PHP**

```php
<?php
$ch = curl_init('https://api.mailblastr.com/audiences/AUDIENCE_ID/contacts/import');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer mb_xxxxxxxxx',
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => <<<'JSON'
{
  "csv": "email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace"
}
JSON,
]);
$response = curl_exec($ch);
curl_close($ch);
echo $response;
```

**Python**

```python
import requests

res = requests.post(
    "https://api.mailblastr.com/audiences/AUDIENCE_ID/contacts/import",
    headers={"Authorization": "Bearer mb_xxxxxxxxx", "Content-Type": "application/json"},
    json={
  "csv": "email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace"
},
)
print(res.json())
```

**Go**

```go
package main

import (
    "fmt"
    "io"
    "net/http"
    "strings"
)

func main() {
    req, _ := http.NewRequest("POST", "https://api.mailblastr.com/audiences/AUDIENCE_ID/contacts/import", strings.NewReader(`{
  "csv": "email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace"
}`))
    req.Header.Set("Authorization", "Bearer mb_xxxxxxxxx")
    req.Header.Set("Content-Type", "application/json")
    res, _ := http.DefaultClient.Do(req)
    defer res.Body.Close()
    out, _ := io.ReadAll(res.Body)
    fmt.Println(string(out))
}
```

**Rust**

```rust
use reqwest::Client;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let res = Client::new()
        .post("https://api.mailblastr.com/audiences/AUDIENCE_ID/contacts/import")
        .header("Authorization", "Bearer mb_xxxxxxxxx")
        .header("Content-Type", "application/json")
        .body(r#"{
  "csv": "email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace"
}"#)
        .send()
        .await?;
    println!("{}", res.text().await?);
    Ok(())
}
```

**Java**

```java
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

var client = HttpClient.newHttpClient();
var request = HttpRequest.newBuilder()
    .uri(URI.create("https://api.mailblastr.com/audiences/AUDIENCE_ID/contacts/import"))
    .header("Authorization", "Bearer mb_xxxxxxxxx")
    .header("Content-Type", "application/json")
    .method("POST", HttpRequest.BodyPublishers.ofString("""
{
  "csv": "email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace"
}
"""))
    .build();
var response = client.send(request, HttpResponse.BodyHandlers.ofString());
System.out.println(response.body());
```

**.NET**

```csharp
using System.Net.Http;
using System.Text;

var client = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Post, "https://api.mailblastr.com/audiences/AUDIENCE_ID/contacts/import");
request.Headers.Add("Authorization", "Bearer mb_xxxxxxxxx");
request.Content = new StringContent(@"{
  ""csv"": ""email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace""
}", Encoding.UTF8, "application/json");
var response = await client.SendAsync(request);
Console.WriteLine(await response.Content.ReadAsStringAsync());
```

**cURL**

```bash
curl -X POST 'https://api.mailblastr.com/audiences/AUDIENCE_ID/contacts/import' \
  -H 'Authorization: Bearer mb_xxxxxxxxx' \
  -H 'Content-Type: application/json' \
  -d '{
  "csv": "email,first_name,last_name\nsteve@example.com,Steve,Wozniak\nada@example.com,Ada,Lovelace"
}'
```

### Response

```json
{
  "object": "list",
  "imported": 1,
  "updated": 1,
  "skipped": 0,
  "total": 2,
  "ignored_columns": []
}
```

`imported` counts net-new contacts; `updated` counts existing contacts merged by email; `skipped` counts malformed rows or conflict-skipped rows; `total` is the sum. `ignored_columns` lists any CSV header names that did not match a registered property and were therefore not stored.

An empty or invalid CSV returns `422 validation_error`. More than 10,000 rows or a body exceeding 5 MB is rejected. An unknown audience returns `404 not_found`. See [Errors](https://www.mailblastr.com/docs/api/errors).