How long does it take Google to reindex my site after I uncheck the box?

Expect anywhere from a few days to a few weeks: Google has to come back and crawl your pages again, which depends on your crawl budget. To speed things up, submit your sitemap in Search Console and request manual indexing of your key pages. Nothing is instant, but a clean site gets re-evaluated far faster.

Does the 'discourage search engines' box actually block Google, or is it just a request?

It's a request, not a wall. The option adds a 'noindex, nofollow' tag that Google respects almost every time, but it carries no legal or technical enforcement. For a real lock, password-protect the site at the server level. During a simple build phase, this request is more than enough.

Should I use a Maintenance or Coming Soon plugin instead to hide my site while I build it?

They solve two different problems. The 'noindex' box hides your site from Google; a Coming Soon plugin hides your content from human visitors behind a holding page. If you want to be both un-indexed and invisible to the public, combine the two: they don't cancel each other out.

Does checking this box also hide the site from visitors, or only from Google?

Only from Google, and even then only from the search engines that honor the tag. Anyone who knows your URL will still see your work-in-progress site as normal. To block humans too, you need a maintenance plugin or password protection: the 'noindex' box does nothing against them.

How to Hide Your WordPress Site from Google While You Build It

Hiding your WordPress site from Google while it’s still being built is strongly recommended for the good organic search ranking (SEO) you’ll want later. Let’s look at how to do it, and why it matters so much.

In concrete terms, this option forces WordPress to add the following meta tag into the head of every one of your pages: <meta name="robots" content="noindex, nofollow"> When Google’s bot lands on your site, this tag immediately tells it that the page it’s on should not be analyzed, and that the internal links on that page should not be followed either. A perfect measure to temporarily block automatic crawling.

Why hide a WordPress site from Google while it’s being built?

When you’re building a WordPress site, several things will hurt your Google ranking for as long as you keep working on it:

Bad permalinks and broken links
The default installed content
Your site’s performance

The problem is simple: if Google has access to your site, it will start grading it from day one… while it’s still a work in progress, so usually empty and far from optimized to welcome visitors. Your ranking will therefore be dragged down right from the start, before your site has even gone live. Let’s see how all of this works, and how to fix it very simply.

What Google really, truly hates: crawling your site for nothing

Google spends a colossal amount of energy crawling the hundreds of millions of websites out there using a very powerful bot, page after page, several times a week, sometimes several times a day. Every website therefore has a crawl budget — the pool of resources Google allocates to come back regularly, crawl your pages, and work out which key phrases they’re relevant for. As it moves through your site, if the bot notices it’s wasting its time on useless pages, or that there are links pointing to pages that no longer exist — creating 404 errors — Google will grade you negatively, and come back to your site less and less often. Google will revise its grade once your site actually goes live. But it won’t change its mind overnight. Trust is earned over time, and by leaving your website open to Google while you’re building it, all you’re doing is spoiling its start… which leads to a ranking that takes far longer to deliver good results.

Problem #1: URLs, permalinks, and broken links

Every web page has an address, called a URL, or a permalink in WordPress jargon. WordPress actually lets you configure the permalinks of your WordPress content to optimize them for SEO, an important part of ranking well on Google. As an example, the URL of the article you’re reading right now is this: https://wooordpress.com/en/hide-wordpress-site-from-google/ A URL is unique to every page on the web, and so becomes the key to reaching it. When Google discovers a page, it memorizes its URL, promising itself it will come back through that same address. The same goes for all your site’s resources, and especially its images. But while a WordPress site is being built, the URL of several pages and images can change (for instance after tweaking your permalink settings, or manually editing a page’s permalink after editing its title) or be deleted outright (after removing a page, a post, or swapping out a photo). When Google tries to come back to the page via its URL, it lands on what’s called a dead link, or broken link — a 404 page Google won’t like. Because if a page changes its URL, Google needs to be told through redirects. And at this stage of building your website, setting up redirects shouldn’t be on your radar yet (Google isn’t supposed to have started its analysis work).

Problem #2: default content and empty content

When you start building a WordPress site, several things are installed automatically along with the system:

a default theme (very often “Twenty Twenty…”), or the theme you’ve just installed
default “demo” content: pages, posts, and comments.

The trouble is, these kinds of content are lexically very thin, often full of Lorem Ipsum (Latin filler text that just pads things out). On top of that, since everyone installing the same theme as you gets the same demo content, it’s duplicated across countless other sites. Your content is therefore of no interest to Google, which will crawl your pages for nothing. It’s also a good idea, for your SEO, to de-index certain types of content that WordPress generates automatically and that add no value (in other words, make them invisible to Google). This is a step that should be done before your site goes live.

Problem #3: your site’s performance

Once a WordPress site is live, plenty of systems are put in place so that pages load as fast as possible for the visitor: server-level caching, WordPress-level caching, a CDN, possibly AMP configuration… But all of these systems are turned off while your site is in development, because they only complicate the work of building and debugging. So it’s obvious that building a WordPress site is a period when pages are likely to load far more slowly than they will after launch. Since page loading speed is among the most important criteria for ranking on Google, this is certainly not the moment for Google to come and visit them.