> For the complete documentation index, see [llms.txt](https://developer.prodege.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.prodege.com/demand/appendix/collecting-user-data.md).

# Collecting User Data

### Using Question Placeholders in `project_url`

The `project_url` field supports **question ID placeholders**, which allow Prodege to dynamically insert a respondent’s answers into your survey URL. Supported question IDs can be found in the `/lookup-question-by-country` endpoint.

#### Placeholder Syntax

Question placeholders use the following format:

```
%q[question_id]%
```

When the URL is generated, each placeholder is replaced with the respondent’s corresponding **option\_id**.

#### Example: Single-Select Question

If you want Prodege to pass a respondent’s **gender** (question ID `3`) into your survey URL, you would include the following placeholder:

```
http://www.yoursurvey.com?your_var_name=%q3%&transaction=%transid%
```

If the respondent’s answer to question `3` is **Male**, and the corresponding `option_id` is `1`, the final URL will be:

```
http://www.yoursurvey.com?your_var_name=1&transaction=145187
```

#### Example: Multi-Select Question

For multi-select questions (for example, question ID `20`: *What languages do you speak?*), multiple answers are returned as a **comma-separated list**.

Original URL:

```
http://www.yoursurvey.com?your_var_name=%q20%&transaction=%transid%
```

If the respondent selected **English** and **Spanish**, with option IDs `1` and `2`, the final URL will be:

```
http://www.yoursurvey.com?your_var_name=1,2&transaction=145187
```

#### Additional Notes

* You may include **multiple question placeholders** in a single `project_url`
* The entire `project_url` field is limited to **2,000 characters**, including all placeholders and parameters