Different behavior between { headless: false } and { headless: true }

I’m curious to know what changes there are between running as headless true vs false. When I run a login to Amazon using headless: true I get an error from Amazon via the screenshot. But when I set headless: false I watch it work just fine, no error.

So I’m trying to figure out what headless: true is doing that is different from when it’s not headless.

Thanks to any suggestions.

[koreus7]

As mentioned in the article @Garbee posted the headless version does not have languages set on the navigator object.

Note also that the headless version will not have languages set in its Accept-Language Header. Some sites (ASP.NET in my experience) require this header to be set. Other sites are looking for this header specifically to identify headless browsers.

I copied the value from an example request generated by my normal chrome install. There is probably a more minimal setting for this header that works.

await page.setExtraHTTPHeaders({
    'Accept-Language': 'en-GB,en-US;q=0.9,en;q=0.8'
});

[jondlm]

For what it’s worth I’ve also found that adding the following user agents override can help smooth over differences in some cases:

await page.setUserAgent('Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.181 Safari/537.36')

The UA I’ve provided is just an example. You can use any valid UA that matches an existing browser.