Keyword blocklists: What they do and whether you should use them

Keyword blocklists are one of the most widely used and most misunderstood tools in digital advertising. The idea is simple: build a list of words and phrases you do not want your brand associated with, and your ads will not appear near that content. In practice, the reality is considerably more complicated.

The advertising industry is in the middle of a significant reckoning with keyword blocklists in 2025 and 2026. The data on over-blocking has become impossible to ignore. An IAS study across four major U.S. media sites found that 72% of content deemed brand-suitable by contextual targeting was still blocked by at least one keyword, and 70% of impressions were unnecessarily blocked. Annualized at a $6.00 eCPM, more than $14 million in viable ad inventory was being suppressed, not because the content was unsafe, but because keywords misinterpreted it.

This does not mean keyword blocklists have no role to play. For email marketing and SMS marketing specifically, blocklists remain essential tools for deliverability and compliance. The nuance is knowing where blocklists are indispensable, where they are blunt instruments, and how to use them intelligently in both contexts.

What are keyword blocklists?

A keyword blocklist is a list of specific words and phrases you are trying to avoid being associated with. Depending on the context, blocklists serve different purposes:

• Programmatic advertising: Prevent your PPC ads from appearing next to or associated with content containing flagged words
• Content marketing: Identify words and phrases to avoid using in your own published content
• Social media: Words and phrases to avoid in posts and captions
• Email marketing: Words to avoid to prevent getting flagged as spam by inbox providers
• SMS marketing: Words to avoid to prevent carrier violations

There are also unique cases that apply to current events and news content.

What are junk email trigger words?

Junk mail trigger words, also known as spam trigger words, are keywords or phrases that email providers consider problematic. Including them will often land your email in the junk folder, regardless of how relevant or legitimate your message is.

Modern spam filters are considerably more sophisticated than simple keyword matching. Today's filters use machine learning to evaluate sender reputation, engagement rates, authentication records, and content patterns together. But problematic keywords still contribute to spam scoring, and avoiding the worst offenders remains worthwhile. Read our guide on 9 tips to help your email get seen for a full approach to inbox placement. For context on how authentication interacts with deliverability, see our guide on preparing for the future of email marketing.

What are carrier violation trigger words?

Carrier violations occur when a mobile phone carrier, such as AT&T or T-Mobile, blocks your SMS message. The blocklist for SMS marketing is more restrictive than email, due to SHAFT laws (Sex, Hate, Alcohol, Firearms, Tobacco), which are strictly adhered to by phone carriers.

For SMS marketing, DailyStory has a built-in deliverability tool to help predict the likelihood of your text message being delivered before you send it.

List of 800+ email and SMS spam trigger words

Get the full list as a Google Sheet or fork it from GitHub. We update it regularly, but recommend following the guidance in this article for selecting which words apply to your specific business rather than using the full list wholesale.

Examples of keywords to block

Some examples of keywords commonly found on blocklists include:

• Cannabis, CBD, Gummies: SHAFT carrier violation for SMS marketing
• Dead, Explosion, Rape: words with negative connotations that trigger spam filters
• Loan, Investment, Viagra: words with associations to financial scams or regulated products

Examples of phrases to block

Some examples of phrases commonly found on blocklists include:

• Guaranteed income: implied guarantee that may be misleading or trigger financial spam filters
• No strings attached: phrases with associations to deceptive offers
• Cancer prevention: potentially misleading health claims

In all the above examples, there are contexts where these words or phrases are entirely legitimate. That is the core challenge with blocklists.

Words and phrases are context-sensitive

The fundamental limitation of keyword blocklists is that they match words, not intent or meaning. A simple example: the keyword "shoot" could be on your blocklist to avoid content about gun violence. But a photoshoot and a school shooting are two very different things. Blocking the word "shoot" would prevent your ad from appearing alongside a fashion photographer's editorial or a sports article about a three-point shot.

IAS's partnership with Reuters found that 54% of URLs cleared as brand-suitable by contextual targeting would have triggered a typical keyword blocklist. Real examples from that study: an article about a film shoot for the upcoming movie "The Devil Wears Prada 2" would have been blocked because its URL contained the word "shot." All of Reuters' content about the band Arcade Fire would be blocked because many keyword tools block URLs containing the word "fire." Premium, brand-safe content, blocked for no legitimate reason.

The COVID-19 case study, and what it taught us

The COVID-19 pandemic provided one of the most instructive large-scale case studies on the costs of keyword over-blocking. When "coronavirus" appeared on blocklists across major advertising platforms, the intent was to protect brands from appearing next to disturbing or polarizing content. In practice, 76% of coronavirus content was actually brand-safe. Advertisers who blocked the keyword missed opportunities to reach audiences across legitimate health news, community updates, and public safety coverage at exactly the moment when those audiences were most engaged.

The same pattern repeated with words like "Black Lives Matter," "election," and "vaccine." Each prompted mass blocklist additions, and in each case the majority of associated content was editorial and brand-suitable. The missed reach was enormous. Simply put, it is the potential of missed opportunities that makes the overuse of keyword blocklists so costly.

Don't use a one-size-fits-all approach

There is no recommended universal approach to keyword blocklists, and a one-size-fits-all blocklist will not serve your business well. A full list of 800+ keywords, like the one we publish, is a starting point and a reference, not a list to adopt wholesale. For any blocklist, you need to narrow the words and phrases down by eliminating ones that are valid or beneficial for your specific business.

Yes, some obvious keywords make sense for nearly every brand. But getting excessive with your list will result in overly restricted advertising, wasted spend, and missed audiences. Think context before expanding your blocklist with keywords that might seem logical at first glance but ultimately appear in perfectly safe content you would be happy to advertise alongside.

Keyword blocklists need to be updated regularly

It is all too common for keyword blocklists to grow over time but never shrink. Keywords get added in response to news events or brand incidents, and then they stay on the list indefinitely, long after the original concern has passed.

Example of an outdated keyword

"Las Vegas" was commonly added to blocklists after the October 2017 mass shooting. Years later, many blocklists still contain "Las Vegas" as a blocked term. For a travel agency, a hospitality brand, or any business targeting entertainment or events audiences, blocking "Las Vegas" is a substantial missed opportunity with no corresponding brand safety benefit. The shooting is historical. Las Vegas as a destination continues to generate enormous amounts of positive, brand-suitable content every day.

Be mindful of context

A travel agency running ads at the same time as major breaking news about Las Vegas would not want to appear alongside distressing coverage. But this is exactly the scenario where contextual targeting outperforms keyword blocking. A contextual tool evaluates the actual content of the page, not just the presence of "Las Vegas" in the URL or copy. It can distinguish between a tourism article and a crisis news report. A keyword blocklist cannot.

Review your blocklist often

Set a regular schedule to audit your keyword blocklists, at minimum quarterly, and more frequently for brands running high-volume programmatic campaigns. For each keyword on your list, ask: does this still represent a genuine brand risk today, or is it a historical addition that no longer applies? Remove keywords that no longer carry the original risk. An actively maintained, minimal blocklist will consistently outperform a sprawling one that has grown unchecked.

Would blocked-content categories suffice?

One key point that is easy to miss in conversations about keyword blocklists is the effectiveness of content blocking at the category level. Most programmatic platforms allow advertisers to exclude broad content categories such as illegal drug content, adult content, hate speech, and violent content. For many brands, category-level blocking alone provides sufficient protection without the over-blocking side effects of keyword lists.

In IAS's 2025 Industry Pulse Report, 49% of media experts said brand suitability is their top media quality priority, and the industry consensus is moving toward contextual intelligence as the primary mechanism, with category blocking as a broad foundation and keyword blocking reserved for genuinely high-risk terms only.

Any additional keyword blocklists beyond category-level blocking carry a real risk of overly restricting where your advertising appears. Missed opportunities and limited campaign reach are the consistent consequences of excessive keyword lists, and the data from IAS, the Brand Safety Institute, and major publishers all confirm this.

The bottom line

The most important consideration is your brand and the context of content your digital advertising could appear alongside. Where are the genuine risks? Where are the missed opportunities?

For email marketing and SMS marketing, keyword blocklists remain genuinely important: deliverability and carrier compliance depend on avoiding flagged words, and the consequences of getting it wrong are direct and measurable. Keep your email and SMS blocklists current and take them seriously.

For programmatic advertising, the calculus is different. Category-level blocking and contextual targeting provide better protection with less collateral damage than keyword lists. If you use keyword blocklists in programmatic, keep the list to a bare minimum of genuinely high-risk terms, review it regularly, and pair it with contextual intelligence rather than relying on it as your primary brand safety mechanism.

Keyword blocklists are a tool that will only be as powerful as the consideration and attention you give them. For more on building a complete digital marketing strategy that accounts for brand safety, deliverability, and campaign performance, see our guides on the difference between programmatic and native advertising, GDPR vs. CCPA and what they mean for your marketing, and carrier violations and what to avoid in SMS marketing.

DailyStory's email and SMS marketing tools include built-in deliverability features, including spam scoring and carrier compliance checks, to help you avoid blocklist triggers before you send. Schedule a free demo to see how DailyStory helps you reach more inboxes and more phones.