A reliable backlink checker is one of the most essential SEO tools for link builders.

But what makes a backlink checker so important?

A website's backlink profile is an essential factor when determining its:

• Domain authority (DA): This is a measure of how likely it is that a website will rank on search engines.

• Search engine ranking: This is how high a website is listed for any given term on a search engine.

3) Ahrefs

• Price: Starts at $79 per month. Free trial available.
• Free version: Yes, with very limited functionality.
• 👉 Try it out here

Ahrefs’ Web Crawler constantly crawls the web to fill its database with new links. It also checks the status of the previously found ones.

Every 24 hours the crawler visits more than 6 billion web pages. It also updates Ahrefs’ index every 15–30 minutes. Ahrefs is home to 12 trillion links, making it the largest database besides Google.

All this link data makes Ahrefs one of the most accurate backlink-checking tools.

What Ahrefs offers

Usually, our first question is, “How many backlinks and referring domains are pointing to my site?”

Put any URL into Site Explorer and Ahrefs will not only give you its external backlinks and referring domains, but also a credible estimate of the domain rating and the site’s organic traffic.

Once you’ve performed a Site Explorer search on a domain or URL, you can use other Ahrefs tools to further analyze its backlink profile.

Comprehensive backlink report

After using Site Explorer, you can access the entire backlink overview of the website or URL by going to “Backlinks.”

What makes Ahrefs’ backlink report so useful is its great filtering and sorting system.

For example, if you want to search for a competitor’s high-quality backlinks, you can:

1. Open the “dofollow” filter and choose to show only the value-passing links.

2. Set the language filter to exclude foreign language links.

3. Sort by the Traffic column to see the links that receive the most traffic.

4. Set the Traffic filter to a value greater than zero to exclude low-quality pages with little or no traffic.

5. Filter the backlink type for “In content,” so that you only see links that are contextual.

You can also use the backlinks section to search your competitors’ backlinks for link building opportunities.

For example, if you’re looking for opportunities to get backlinks from resource pages, simply type “resources” in the backlinks search. This will show you which resource pages are linking to your competitors.

And if they are willing to link to your competitors, they’ll probably be interested in linking to your site.

The versatility of the backlink report makes it a useful tool for monitoring the health of your backlink profile. It can be used to:

• Find broken links.

• Find low-quality backlinks coming from “spammy” websites.

• Spot over-optimized anchor text.

Monitor backlink profile changes

The New Backlinks function shows you the number of links a site has gained or lost over a period of time.

With Ahrefs’ web crawler continuously updating its link profile, you should be able to accurately monitor the daily changes in backlinks to your website.

Each day's backlinks are displayed using a calendar view at the top of the report.

Ahrefs makes backlink monitoring easy by letting you set an email alert to notify you of new and lost backlinks.

Find competitors’ backlinks

The referring domains report offers a list of domains that have one or more backlinks to the target site or URL.

You can use it to find your competitors’ serial linkers (domains that link to the same website repeatedly).

By identifying your competitors’ serial linkers, you are finding people that are interested in linking to topics similar to your own. Building relationships with them can lead to beneficial link building opportunities.

An easy way to find them is to look for referring domains with 10–50 links to the competing site.

Sort by the “Links to target” column with the “dofollow” filter on.

You can delve deeper by looking at the actual backlinks from each site. Hit the down arrow under the “Links to target” column to do this.

The Referring domain report is also useful for finding potentially spammy backlinks. You can choose to disavow these links—this is when you tell Google to not count them towards your rankings.

To do this, sort your referring domains by Domain Rating (DR), from lowest to highest.

Low DR doesn’t necessarily mean that the site is spammy, so you’ll need to investigate each backlink manually. Look for “spammy” signals, like:

• Spammy sounding domains, like xcoinage.surf

• Lots of foreign domains, like those ending .cn or .ru

• Sites that obviously don't belong to your niche.

Once you have spotted a suspicious site, click the “Links to target” arrow.

The first thing you should do is to look at the anchor text of the link. If it looks suspicious, incoherent, or doesn't coincide with your niche, it’s likely a spam link.

You can also click on a suspicious link to check if the content on that page is of low quality.

The referring domains graph is a useful visualization for monitoring your competitor's backlink acquisition rate; are they growing or losing backlinks?

Look for spikes in backlink acquisition, and find content that they produced or improved during that period of time. This is useful for identifying content ideas you could use on your own site.

The referring domains graph is also useful for pinpointing possible negative SEO attacks.

Find link opportunities

Want to know who’s linking to your competitors, but not to you?

The Link Intersect tool builds a list of viable link opportunities by finding pages that link to your competitors, but not to you.

This lists all the possible backlinks your competitors have accumulated. You can enter up to ten competitors.

Compare your domain against competitors

Using the Domain Comparison tool, you get a side-by-side view of how your site weighs up against your competitors on Domain Rating, backlinks, referring domains, and more.

See how competitor pages perform

By using the “best by links” report, you can see which of your competitor’s pages is performing the best and getting linked to the most.

This is incredibly useful for giving you ideas on what they’re getting right and where you can improve.

Find which pages attract links

Ahrefs tells you which pages have received the most visitors over the last day, week, or month thanks to your backlinks.

In other words, it shows who has made the biggest efforts to promote your content.

What are the downsides of Ahrefs?

Ahrefs only letdown is on link quality.

They don't really have a system to flag potentially spammy or harmful links, like Moz’s Spam Score.

Ahrefs instead provides all the relevant data so that you can do a manual review of backlinks.

Let’s go through some of the other backlink checker tools.

Though Ahrefs gets our badge of approval, these other mentions are all great backlinking tools that have their own merits.

4) Semrush

• Price: Starts at $119.95 per month. Free trial available.
• Free version: Yes, with limited functionality.
• 👉 Try it out here

Semrush’s backlink checker is very similar to Ahrefs in many ways. In fact, many people prefer it.

It has a massive index of backlink data, and lots of features, including:

• Authority Score. This is Semrush's name for domain authority metrics.

• Breakdown of anchor text.

• Number of links received over time.

• Dozens of filters to refine your search.

What Semrush offers

Semrush’s backlink tool has a few cool features that Ahrefs doesn’t.

For example, Semrush actually breaks a site’s referring domains into different categories.

It also shows you a list of sites that have similar profiles to yours.

This is incredibly useful for launching a new link building campaign because if they have similar profiles to you, they’re most likely getting links from the same places you want to.

5) Moz

• Price: Starts at $99 per month. Free trial available.
• Free version: No.
• 👉 Try it out here

Moz’s Link Explorer tool is an incredibly useful backlink checking tool.

When using Link Explorer, for each backlink you’ll be able to view:

• Anchor text.

• URL.

• Domain authority (DA).

• Page authority (PA).

• The number of unique external linking domains.

• The date the link was first seen.

• The date the link was lost (if applicable).

• Link target.

• Spam score.

What Moz offers

The Spam Score is a useful feature. It measures the percentage of websites with similar characteristics to those that have been penalized by Google.

This helps you to make easy calls about the quality of your backlinks based on the Spam Score of the sites they originate from.