# Tracking Pixels

Treasure Data users can use data from a tracking pixel to send events to Treasure Data.

**Contents**

* [Prerequisites](#prerequisites)
* [Preparing the URL](#preparing-the-url)
  * [Authentication](#authentication)
  * [Parameters](#parameters)
* [Use with <img> Tag](#use-with-img-tag)


## Prerequisites

* Basic knowledge of Treasure Data


## Preparing the URL

You must set up authentication and specify a path before you can add the postback that is used by Treasure Data.

### Authentication

Every request must contain *authentication information*, provided by the special `td_write_key` URL parameter. The API key can be retrieved from TD Console. It's recommended to use [write-only API key](/products/my-settings/getting-your-api-keys).


```
https://in.treasuredata.com/postback/v3/event/{database}/{table}?td_format=pixel&td_write_key=XXXYYYZZZZ&...
```

### Parameters

Specify these two parameters within a path.

* `{database}`: specify the destination database name in the URL. Only alphabet, numbers, or _ are allowed.
* `{table}`: specify destination table name in URL. only alphabet, numbers, or _ are allowed.


Any URL parameter, except special parameters listed as follows, is considered as a column inside the record.

* **td_format**: Specify `pixel`
* **td_write_key**: As described in Authentication.
* **td_record_time**: Specify a UNIX timestamp value to set time column in Treasure Data. If it's not specified, the time records that are received are used.
* **td_global_id**: If `td_global_id=td_global_id` in the query string of postback URL is added, then the API adds a column named `td_global_id` with value of actual td_global_id into the record.
* **td_ip**: If `td_ip=td_ip` in the query string of postback URL is added, then the API adds a column named `td_ip` with the value of source IP into the record.
* **td_ua**: If `td_ua=td_ua` in the query string of postback URL is added, then the API adds a column named `td_ua` with the value of actual user-agent into the record.
* **td_redirect**: The API can redirect to the specified URL. The URL must be encoded. If the td_redirect value includes td_global_id as a parameter, then the API replaces it with an actual value.


All parameter values are considered as *strings*, and you cannot change the value type at the ingestion time with a tracking pixel.

For example URL structure would be something like this:


```
https://in.treasuredata.com/postback/v3/event/{database}/{table}
  ?td_format=pixel
  &td_write_key=XXXYYYZZZZ
  &td_global_id=td_global_id
  &td_ip=td_ip
  &td_ua=td_ua
  &your_custom_key1=val1
  &your_custom_key2=val2
  &your_custom_key3=val3...
```

## Use with <img> Tag

Use the URL with an **img** HTML tag as the postback to Treasure Data.


```html
<img src="https://in.treasuredata.com/postback/v3/event/{database}/{table}?td_format=pixel&td_write_key=XXXYYYZZZZ&td_global_id=td_global_id&td_ip=td_ip&td_ua=td_ua&key1=val1&key2=val2&key3=val3..." />
```

Using image tags for tracking in emails is not suggested. This is because emails containing tracking tags from a domain different from the email sender's domain are more likely to be flagged as spam.

Additionally, in recent years, platforms like Apple have started treating open tracking as always open by default, reducing the effectiveness of pixel-based open tracking. Consider a broader marketing strategy that includes directing recipients to landing pages and other engagement methods.