Link building is the part of search marketing with the widest gap between the best and worst providers, because the output looks superficially identical: a spreadsheet of URLs pointing at your site. One agency earned those placements by making something worth citing and persuading an editor. Another bought them from a network that sells the same slot to everyone. Both will send you a report. This page sets out what distinguishes the agencies worth shortlisting, what Google's published policies actually prohibit, and the specific questions that reveal which kind of firm you are talking to before the invoice arrives.
What the good ones actually sell
A serious link building agency sells two things: an asset and a relationship. The asset is something a publisher has a reason to reference, which in practice means original data, a genuinely useful tool or resource, expert commentary a journalist can quote, or a story about your business that is interesting to someone who does not work there. The relationship is the outreach capability, meaning people who know which writers cover the subject and can pitch without being ignored. Firms that have neither fall back on the only thing left, which is paying for placement. That is why the most useful question in a pitch is not how many links per month but where the last ten came from, who at your firm made them happen and what made the publisher say yes. A firm that cannot answer that with specifics is reselling inventory.
What Google's policies actually prohibit
Google's spam policies define link spam clearly enough to use as a purchasing standard. Buying or selling links for ranking purposes is named, including exchanging money, goods or services for links, and sending a free product in exchange for a link. Excessive link exchanges, large-scale article marketing and guest posting campaigns with keyword-rich anchor text, and automated link creation are all named. Advertorials and native advertising carrying links that pass ranking credit are named too. Google's remedy is not secret: links that exist because of payment should be qualified with rel sponsored or rel nofollow, which removes the ranking value. Sites that violate the policies may rank lower or not appear in results at all. That is the risk you take on, not the agency, so any provider should be willing to describe its sourcing in writing before you sign.
Questions that separate the two kinds of firm
Ask where the last ten links came from, by name. Ask whether any money, product or service changed hands for any of them, and take a vague answer as a yes. Ask who writes the content that gets placed and whether you may see three examples with bylines. Ask what proportion of outreach targets reply, since real outreach has a low and honest hit rate while networks have a suspiciously high one. Ask what happens to the links if you stop paying, because links that vanish on cancellation were rented rather than earned. Finally, ask them to explain, in their own words, what Google's spam policies say about paid links. A firm that has not read them is not equipped to keep your site out of trouble, and a firm that has read them and sells them anyway is choosing your risk for you.
What moves the price, and what a fair deal looks like
Price tracks difficulty rather than volume. A link from a publication with an editorial standard costs more than one from a site that publishes anything, because the work behind it is real: research, writing, pitching and follow-up. Beware pricing that is quoted purely per link with a domain metric attached, since that structure only makes sense if links are inventory being resold. Prefer a retainer against a defined programme of asset creation and outreach, with reporting that names every placement and how it was obtained. Ask for a clause requiring disclosure of any paid placement. Link building is usually bought as one line inside a wider search engagement, so if you are also evaluating link building companies against a full-service agency, compare on sourcing transparency first and volume last.
Questions people ask about top link building agencies
Is paying for links against Google's policies?
Buying or selling links for ranking purposes is named as link spam in Google's spam policies. Paid placements are allowed as advertising when the links are qualified with rel sponsored or rel nofollow, which removes the ranking benefit. Sites that violate the policies may rank lower or not appear at all.
How many links per month should an agency deliver?
Volume is the wrong unit. A handful of placements on publications with editorial standards will do more than dozens from sites that publish anything. Judge a programme on where links come from and how they were obtained, and treat a guaranteed monthly quota as a sign that inventory is being resold.
What is a fair price for link building?
Prices track the difficulty of earning the placement rather than a per-link rate card. Prefer a retainer covering asset creation and outreach with named placements reported, over a per-link price attached to a domain metric, which is the pricing shape of a reseller.
Can bad links get my site penalised?
Google's spam policies state that sites violating them may rank lower or not appear in results. The exposure sits with your domain, not with the vendor, which is why sourcing transparency belongs in the contract and why you should be able to see where every placement came from.