Why do hidden links in emails get high click rates from bots and automated systems?
Matthew Whittaker
Co-founder & CTO, Suped
Published 20 May 2025
Updated 19 Aug 2025
7 min read
It can be perplexing to see your email campaigns register a high volume of clicks on links that are deliberately made invisible to human recipients. I've encountered situations where a hidden image link, unnoticeable to the casual eye without inspecting the HTML, showed thousands of unique clicks, far surpassing the actual open rates. This phenomenon points towards automated systems rather than human interaction.
These seemingly anomalous click rates are not only normal in today's email landscape but also a direct consequence of how email security and filtering mechanisms operate. Understanding these automated interactions is crucial for accurate email metric analysis and overall deliverability strategy.
Why bots click hidden links
Hidden links, often embedded within tiny images or obscured in the email's HTML, are prime targets for bots because these automated systems scan emails comprehensively, regardless of visual presentation. Their primary directive is to protect recipients from potential threats. This means they will follow every link they find, visible or not, to check for malicious content, phishing attempts, or spam, affecting your recorded email click data. This process happens before the email even reaches a human inbox, leading to what appear to be immediate, high click-through rates, distorting your email analytics and potentially leading to inflated click-through rates.Robot clicks are a common challenge in email metrics.
The difference in click rates between image links and standard website links, as you observed, might be due to how specific mail clients or security solutions prioritize or process certain content types. For instance, some systems might aggressively pre-fetch or scan image URLs more thoroughly than other link types, especially if the image itself is hosted on an unfamiliar domain. It's also possible that the exact way the link is hidden (e.g., zero-width spaces, tiny font size, or off-screen positioning) makes it particularly susceptible to automated detection methods.
These are not clicks from human subscribers, but rather from security software designed to keep inboxes safe. If you're using hidden links as a form of honeypot to identify bots, then these high click rates confirm that the automated systems are indeed active and performing their intended function. This is a common method to help identify bot clicks in email marketing campaigns.
Understanding bot behavior
Automated systems don't render emails visually in the same way human users do. They parse the raw HTML, extracting and validating all URLs present. A link hidden by CSS or tiny dimensions is still a valid HTML element that a bot's parser will detect and interact with.
Security scanning: Email security gateways and spam filters (like those from Google or Microsoft) employ bots to scan incoming messages for suspicious links before delivery. This prevents malware or phishing from reaching the recipient's inbox, even if the user clicks on a malicious link.
Link validation: Many email clients and internet service providers (ISPs) use automated systems to validate all URLs within an email. This includes checking if the link is active, leads to a legitimate page, or triggers any known security warnings.
Honeypot detection: Some senders intentionally use hidden links as honeypots. If these links are clicked, it signals bot activity, allowing the sender to segment out non-human interactions from their engagement metrics.
Types of automated systems
The types of automated systems that engage with email links vary, but they generally fall into categories designed for security, content analysis, or compliance. These systems are constantly evolving to combat sophisticated phishing and malware threats, which often rely on hidden or disguised links to evade detection.
Even for B2C lists, where you might expect fewer enterprise-level filters, many consumer-facing email providers like Gmail and Yahoo also employ robust pre-scanning mechanisms. Outlook's Safe Links feature, for example, is notorious for automatically clicking and rewriting URLs. This means a significant portion of your inflated clicks could stem from these protective measures.
The very nature of how these bots operate means they don't differentiate between a visible link meant for human interaction and a hidden one. Their goal is to programmatically inspect all elements. This is why a hidden image link, which no human would intentionally click, can still accrue thousands of clicks from these automated systems, leading to inflated click metrics for email campaigns.
Bot/System Type
Primary Function
Impact on Clicks
Email security gateways
Scan for malware, phishing, and spam before delivery.
Proactively click all links, including hidden ones.
Link preview/validation services
Generate previews or validate URLs for safety.
May fetch content from all links to create snippets.
Anti-spam bots (general)
Identify spam tactics, including obscure link usage.
Trigger clicks on any link, regardless of visibility.
Impact on email metrics
The most immediate consequence of these bot clicks is the skewing of your email engagement metrics. A hidden link that racks up thousands of clicks can make your campaign appear far more successful than it actually is, leading to misinformed strategic decisions. This makes it difficult to assess true subscriber engagement and the effectiveness of your calls to action.
While a high click rate from bots might seem harmless, it can complicate understanding your audience's behavior. If you're A/B testing different content or subject lines, false clicks can obscure the real impact of your changes. It's essential to differentiate between genuine human engagement and these automated interactions to properly gauge your email marketing performance.
This challenge highlights the importance of robust data analytics and the ability to filter out non-human interactions. Recognizing that these clicks are part of a broader email security ecosystem is the first step towards accurate reporting and optimizing your campaigns.
Before mitigation
Inflated metrics: Click-through rates appear artificially high, making it seem campaigns are performing better than they are. Your email metrics are distorted.
Misleading A/B tests: Difficult to determine winning variations when bot clicks contaminate results.
Poor resource allocation: Teams might invest in strategies based on false engagement data.
After mitigation
Accurate reporting: Real click-through rates reveal actual subscriber behavior.
Informed decisions: Campaigns are optimized based on genuine engagement metrics.
Improved sender reputation: Better understanding of engagement leads to better list hygiene and deliverability.
Identifying and mitigating bot clicks
While it's impossible to completely prevent bots from scanning your emails, you can implement strategies to identify and mitigate their impact on your data. The goal is not to stop the security scans, but to gain clarity on your true human engagement. For instance, you can use honeypot links (like the hidden image link you described) to specifically flag bot activity.
Many email service providers (ESPs) are now implementing features to automatically filter out or flag bot clicks. However, if your ESP doesn't offer this, you can look for patterns in your click data: rapid clicks within seconds of delivery, clicks from data center IPs (like Amazon Web Services or Microsoft Azure), or clicks from unusual user agents. Identifying these patterns is key to understanding the true engagement of your subscribers and knowing how to combat spam filter and bot clicks.
For more advanced analysis, some tools allow you to access raw click data, including IP addresses and user agents, which can help you manually or programmatically segment out non-human interactions. This is a crucial step towards avoiding false email click data.
Always monitor your email metrics for sudden, uncharacteristic spikes in click rates.
Segment bot clicks from human interactions to gain accurate insights into campaign performance.
Use a dedicated, invisible honeypot link to explicitly identify bot activity and filter it out.
Understand that high bot clicks often indicate robust email security, not necessarily malicious intent.
Cross-reference click data with other engagement metrics, like website visits or conversions.
Common pitfalls
Assuming all clicks are from humans, leading to inaccurate campaign performance assessments.
Failing to account for the impact of security systems on your reported click-through rates.
Ignoring bot click data, which can obscure true subscriber engagement and campaign effectiveness.
Over-optimizing campaigns based on inflated click metrics from automated systems.
Not configuring your ESP to differentiate between human and non-human interactions.
Expert tips
Analyze user-agent strings and IP addresses associated with clicks to distinguish bots from human users.
Employ DMARC reports to get a clearer picture of email authentication and potential spoofing attempts.
Consider the timing of clicks; bot clicks often occur within seconds of email delivery.
Implement methods to prevent automated systems from signing up for your mailing lists.
Periodically review your email list hygiene to remove inactive or bot-generated addresses.
Marketer view
Marketer from Email Geeks says that if most subscribers are B2B inboxes, enterprise filters often click links to see where they go, and suggested checking for common user agents.
2019-08-11 - Email Geeks
Marketer view
Marketer from Email Geeks mentioned that some email service providers track browser usage and IP addresses, which can help trace bot clicks back to their source, like Barracuda or Office 365.
2019-08-11 - Email Geeks
Navigating automated email interactions
The high click rates on hidden links are a clear indication of automated systems at work, diligently scanning your emails for security threats. This is a common and expected behavior in the modern email ecosystem, driven by the need to protect users from malicious content. While it can complicate your metric analysis, it's a testament to the robust security measures in place across various email providers.
By understanding the role of these bots and implementing strategies to identify and filter their activity, you can gain a more accurate view of your email campaign performance and improve your overall email deliverability. Focus on the engagement metrics that truly reflect human interaction to make informed marketing decisions.
Google or 
Microsoft) employ bots to scan incoming messages for suspicious links before delivery. This prevents malware or phishing from reaching the recipient's inbox, even if the user clicks on a malicious link.
Yahoo also employ robust pre-scanning mechanisms. 
Outlook's Safe Links feature, for example, is notorious for automatically clicking and rewriting URLs. This means a significant portion of your inflated clicks could stem from these protective measures.
