Understanding Why WinHTTPRequest ResponseText Differs in MsgBox and Debug.Print

Discover the reasons behind different outputs when using `WinHTTPRequest` in VBA with `MsgBox` and `Debug.Print`. Learn how to properly handle the response for dynamic web pages!
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This video is based on the question https://stackoverflow.com/q/75569073/ asked by the user 'Pete Marise' ( https://stackoverflow.com/u/12771124/ ) and on the answer https://stackoverflow.com/a/75569223/ provided by the user 'Tim Williams' ( https://stackoverflow.com/u/478884/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Exploring the Variances in WinHTTPRequest Response Values

If you've ever delved into programming with VBA and WinHTTPRequest to retrieve data from web pages, you may have stumbled upon a perplexing issue: the differing outputs of responseText when viewed in a MsgBox versus printed in the Immediate pane using Debug.Print. Let's break down this curious phenomenon to gain a clearer understanding of what's happening behind the scenes.

The Initial Problem

Our journey begins with an unexpected result encountered while attempting to pull data from a dynamic web page using WinHTTPRequest. The user noticed that while the contents displayed in a message box were complete and reminiscent of the webpage's source code, the output seen in Debug.Print was quite different and somewhat truncated. Instead of proper HTML and JavaScript, it returned a message indicating an issue with scraping a QuickBase page.

Code snippet illustrating the issue:

[[See Video to Reveal this Text or Code Snippet]]

This led to the question: "Why does WinHTTPRequest’s responseText return a different value to MsgBox than to Debug.Print?"

Understanding What's Going Wrong

The Limits of Debug.Print

Size Limitations:

When you send a long string to the Immediate pane (using Debug.Print), it only displays the last 200 lines or so. This presents a fundamental limitation when trying to visualize longer outputs or responses.

This could be why certain elements of the response appear missing or are truncated.

Content Display Differences:

MsgBox can only accommodate approximately 1024 characters. Therefore, if your response text is longer than that, you might not be seeing the complete output, which can lead to confusion regarding what data is genuinely available.

Spreadsheet Cell Size:

If trying to paste the results into a cell, be aware that the maximum length allowed in an Excel cell is about 32,767 characters. Anything beyond that will be cut off.

Implications of Dynamic Content

Dynamic web pages often load content using JavaScript or other methods that might not be captured during a basic HTTP request. This can result in receiving different layers of HTML, depending on how the server processes the request, especially if content is generated dynamically.

Conclusion

The discrepancies between the outputs observed in MsgBox and Debug.Print primarily arise from the inherent limitations of both methods when dealing with large or complex responses from WinHTTPRequest.

Key Takeaways:

Know the Limits: Always consider the character limits when displaying output in MsgBox or through Debug.Print.

Use Alternative Methods for Long Outputs: Consider writing the results directly to a file or an Excel cell if the data is expected to surpass the limits of these tools.

Understand Your Data Source: When scraping dynamic web pages, ensure you recognize the potential issues associated with JavaScript rendering and how that data is served.

By understanding these nuances, you can better manage how you handle web responses in your VBA projects, ensuring a more seamless coding experience.

If you have any further questions or need additional clarification regarding these concepts, feel free to reach out!

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