Do you really need a robots.txt file to control your site's indexing?

Is the robots.txt really optional or is this a simplification?

Google states that the robots.txt file is not essential. Technically, this is true: a site can function without it. But this statement deserves nuance.

The absence of a robots.txt means that all paths on the site are crawlable by default. For a 50-page blog, no problem. For an e-commerce site with thousands of filtered pages, dynamically generated URL parameters, or publicly accessible admin sections, it's a different story.

What really happens when a site has no robots.txt?

Googlebot will attempt to crawl all URLs it discovers, whether through internal linking, sitemaps, or backlinks. If your site generates URLs on the fly — facet filters, user sessions, infinite pagination — the crawler can get lost in an almost infinite loop.

Result: waste of crawl budget on pages with no SEO value, to the detriment of strategic pages. Small sites may get away with it, but once you exceed a few hundred pages, the absence of a robots.txt becomes a structural handicap.

What are the limitations of control via robots.txt?

The robots.txt blocks crawling, not indexing. This is a common confusion, even among experienced SEOs. A URL blocked in robots.txt can still appear in search results if external links point to it.

Google will then display an empty snippet with just the URL. To actually prevent indexing, you need to combine robots.txt with a noindex meta tag or an X-Robots-Tag header — but beware, if you block crawling before Google sees the noindex, it won't work.

• Robots.txt controls crawling, not indexing — it's a crawling directive, not a publishing one.
• The absence of robots.txt equates to a global Allow: / — everything is accessible, without filter.
• Sites with dynamic URLs (e-commerce, UGC platforms) desperately need a robots.txt to avoid wasting crawl budget.
• A poorly configured robots.txt can block strategic sections — regularly checking via Search Console is essential.
• Combining robots.txt and noindex requires precise logic: the crawl must be temporarily accessible so that Google sees the noindex tag.

Is this statement consistent with real-world observations?

Yes, but it is deliberately simplified. Google isn't lying: technically, a site does operate without a robots.txt. But saying it's 'not essential' is like saying a steering wheel isn't essential for driving — technically true if you're going straight, catastrophic as soon as you hit a turn.

In practice, the majority of audited sites with crawl budget issues either have no robots.txt or a poorly configured one. Modern crawlers (Googlebot, Bingbot) are powerful, but they do not guess which sections of your site are strategic. It's up to you to guide them.

What nuances should be added to this statement?

Google does not specify that the absence of a robots.txt can mask structural errors. If your site generates thousands of junk URLs through poorly managed parameters, the absence of a robots.txt won't directly cause a penalty — but it will lead Googlebot to waste time on unnecessary content.

[To verify]: Google states that 'all pages can be crawled by default' without a robots.txt, but says nothing about the crawl priority order. Will a site without robots.txt be crawled uniformly, or will Googlebot favor popular sections? Observations suggest that the crawler prioritizes areas with backlinks and strong internal linking, but Google does not explicitly document this logic.

When does this rule become problematic?

For sites with aggressive pagination, e-commerce facets, or dynamically generated content, not having a robots.txt is a strategic mistake. Modern crawlers can detect some loops, but not all — and the time wasted on these sections mechanically reduces the crawl of important pages.

Another case: sites with publicly accessible private sections that have no SEO value (member areas, carts, user accounts). Without a robots.txt, Google may index these URLs, creating noise in search results and diluting the overall domain relevance.

What should you actually do with your robots.txt file?

First, create a robots.txt even if it's minimalist if your site doesn't have one. An empty file or one with just a User-agent: * and a Sitemap: is already better than nothing — it indicates to Google that you are actively managing your crawl.

Next, identify the sections to block: admin, facet filters, session URLs, tracking parameters (utm_, ref=, etc.). Use server logs or Search Console to identify URLs that are being crawled unnecessarily.

What mistakes should you absolutely avoid?

Never block critical resources (CSS, JavaScript, images) in robots.txt. Google needs them to evaluate the complete rendering of the page. Blocking /wp-content/ or /assets/ may seem logical to 'hide' your CMS, but it hampers indexing.

Another common mistake: blocking a section with Disallow while hoping it won't be indexed. Robots.txt does not deindex. If you want to remove URLs from the index, you need a noindex or a removal via Search Console — and temporarily keep the crawl accessible so that Google sees the directive.

How to check that my robots.txt is working correctly?

Use the robots.txt testing tool in Search Console. It simulates the crawl and shows you if a URL is blocked or not. Check regularly, especially after a migration or structural change.

Also compare the URLs crawled in coverage reports with your robots.txt. If Google is massively crawling sections you thought were blocked, there’s a discrepancy — often due to poorly placed wildcards or contradictory directives.

• Create a minimal robots.txt with User-agent: * and reference to the XML sitemap
• Block admin sections, URL parameters, and unnecessary facet filters
• Never block CSS, JS, or image resources necessary for rendering
• Test each modification using the Search Console tool before deploying it to production
• Monitor server logs for detecting URLs crawled unnecessarily
• Combine robots.txt and noindex for pages to exclude from the index, keeping crawl accessible temporarily