Explaining rel canonical HTTP header
A rel canonical HTTP header is a Link response header naming the preferred URL for a file, used for PDFs and other non-HTML files. Google adopted it in 2011.
Decoded
Reference articles that each go deep on a single ad tech term. Every entry in the Explaining series opens with a plain-language definition, then covers the mechanics, origins, key dates, limitations, and commonly confused adjacent terms - grounded in PPC Land coverage, platform documentation, and industry standards from bodies like the IAB.
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Explaining phishing
Phishing is a cyberattack that uses fake emails, texts, calls or ads posing as trusted brands to trick people into handing over passwords or sending money.
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Explaining App Tracking Transparency
App Tracking Transparency is Apple's iOS permission system that makes apps ask before tracking users across other companies' apps and sites for advertising.
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Explaining CarPlay
CarPlay is Apple's system for projecting a simplified iPhone interface onto a car's dashboard, launched in 2014 and now contested by GM and other carmakers.
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Explaining attention per mille
Attention per mille (APM) counts the seconds of human attention an ad earns per 1,000 impressions, letting buyers compare formats on looking, not on serving.
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Explaining frequency illusion
Frequency illusion, or the Baader-Meinhof phenomenon, is the bias where something newly noticed seems to appear everywhere, shaping how ad repetition feels.
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Explaining eye tracking
Eye tracking measures where a person looks and for how long using cameras; in advertising it shows whether ads are seen and trains attention prediction models.
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Explaining purchase intent
Purchase intent is a measure of how likely a person is to buy a product, captured in surveys or inferred from searches and browsing to target and measure ads.
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Explaining cumulative attention
Cumulative attention is the total seconds of attention one person gives a campaign's ads across all exposures, an attention-era rethink of effective frequency.
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Explaining ACH
ACH, the Automated Clearing House, is the US bank network that moves payroll, bills and ad spend between accounts in batches, cheaper and slower than cards.
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Explaining acqui-hire
An acqui-hire is a deal done mainly to hire a startup's team, now often a licence-plus-hiring pact used by AI firms and examined by competition authorities.
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Explaining COBRA
COBRA is the 1986 US law letting workers who lose job-based health cover keep the same group plan for 18 to 36 months, paying up to 102% of the total cost.
