> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pdf.co/llms.txt
> Use this file to discover all available pages before exploring further.
# Welcome to PDF.co API Tester
> The API Tester helps you quickly explore and test our API endpoints. You can send real requests, check responses, and estimate credit usage, all in one place. It's the fastest way to understand how our API works before you integrate it into your own app or workflow.
## Getting Started
To begin testing, you'll need an API Key.
* If you already have an account, [log in](https://app.pdf.co/login) to retrieve your key.
* If not, [sign up](https://app.pdf.co/signup) and receive 10,000 free credits to start exploring the endpoints.
For detailed instructions and examples, see the [Authentication Guide](/api-reference#authenticating-your-api-request).
## URL Input
Our API supports files from any public link, such as Google Drive, Dropbox, and others. However, third-party storage providers may restrict the number of requests to their files, which can cause errors during processing. To prevent this, we recommend using our File Upload endpoint to store files in [PDF.co's built-in storage](https://app.pdf.co/tools/files). For details, see our [File Upload guide](/api-reference/file-upload/overview).
## **Response Codes**
When you run a request, the tester will return both the **output data** and the **response code**. Common codes include:
| Error Code | Description |
| :--------- | :------------------------------------------------------------------------------------------------------------------------------- |
| `200` | Success. |
| `400` | Bad request. Typically due to bad input parameters or unreachable input URLs (e.g., access restrictions like login or password). |
| `401` | Unauthorized. Authentication is required and has failed or has not yet been provided. |
| `402` | Not enough credits. |
| `403` | Access forbidden for input URL. |
| `404` | The requested resource could not be found. |
[**See Full List of Response Codes**](/api-reference/response-codes)
## Credit Usage
Every API call costs credits. The amount depends on the specific endpoint you're using and the size of your file. Use our [**Credits Calculator**](https://app.pdf.co/subscriptions#credits-calculator) to estimate usage before sending requests.
## Working with Async Mode
:bulb:Tip: For larger or long-running tasks (over 30 seconds), use async mode to avoid timeouts and optimize credit usage. Set the `async` parameter to true when making your request. The API will return a `JobID` and an empty URL, you can then use the [Job Check endpoint](api-tester/job-check) to retrieve the results once processing is complete. Learn more in the [**Sync and Async Mode Guide**](/api-reference/async-and-sync-mode).
## Test Your Endpoint
You can try out some of the most popular endpoints right here. Simply choose an endpoint, click **Try It**, and provide the file URL you want to process.
Process invoices faster than ever by extracting data and structuring it
automatically with our advanced AI. Get quick and accurate data from any
invoice, no matter the layout.
Add text, images, forms, other PDFs, fill forms, links to external sites and
external PDF files. You can update or modify PDF and scanned PDF files.
Compress PDF files to reduce their size.
Convert PDF and scanned images to text with layout preserved. This method uses
OCR and reporoduces layout.