Hidden Text & Prompt Injection Detector
Scan files and text for hidden prompts before they reach your AI tools.
Detect invisible text, suspicious instructions, metadata-based risks, and unsafe embedded content in one place. Sanitize PDFs before summarizing, drafting, searching, or passing them into an AI workflow.
The file may be damaged, password-protected or saved in an unusual format. Open it, save a fresh copy as PDF, and upload that.
Its pages are images, so there’s no text layer to check. Ask for the original file, or download the assignment again as a regular PDF instead of a photo or scan.
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This PDF has instructions an AI tool will read and follow, but you won’t see them on the page.
These lines are invisible when you read the PDF, but an AI tool will read and follow them.
Create a free account to read each hidden prompt in full.
Subscribe to read the hidden prompts in this file and every one after it.
See plansThis report covers the text we could read from the PDF. It isn’t a 100% guarantee the file has no other hidden prompts.
Humanio turns your AI-assisted draft into natural, human-sounding writing.
This report covers the text we could read from the PDF. It isn’t a 100% guarantee the file has no other hidden prompts.
Humanio turns your AI-assisted draft into natural, human-sounding writing.
- Detect hidden prompts and invisible text
- Sanitize PDF files before AI processing
- Reduce prompt injection risk in uploaded documents
What Is a Prompt Injection Detector?
A prompt injection detector helps you find instructions inside text or files that are meant to manipulate an AI system. Those instructions are not always obvious. They can appear as hidden text, invisible Unicode characters, metadata, comments, embedded content, or prompt-like commands buried inside a document.
Instead of assuming every upload is safe, you check the content first, flag suspicious elements, and clean the file before it reaches your model.
Why Hidden Prompt Detection Matters
AI systems often process more than what a person sees on the screen. A file can look harmless while still containing instructions that try to override user intent, leak information, or push the model toward unrelated actions.
That risk shows up in places like:
- pasted text
- PDFs
- hidden or invisible text
- comments and tracked changes
- custom XML and metadata
- encoded or obfuscated instructions
If your workflow involves uploads, external documents, or copied content, prompt injection protection should happen before the AI reads the input.
Detect Hidden Text and Suspicious Instructions
Some prompt injection attempts are direct and easy to spot. Others are designed to stay out of sight while still being readable by AI systems.
A strong detector should help you identify:
- invisible or low-visibility text
- zero-width and non-printing characters
- white-on-white or hidden formatting
- suspicious instruction phrases
- encoded payloads
- prompt-like commands inside metadata
- hidden comments, XML, or embedded content
This gives you a clear way to review risky input before it becomes part of your AI workflow.
Sanitize PDFs Before AI Processing
PDFs can contain more than visible page content. They may also carry metadata, comments, hidden layers, embedded files, attachments, scripts, and other elements that should not pass into an AI system unchecked.
With PDF sanitization, you can:
-
scan uploaded PDFs for hidden risks
-
detect suspicious content before ingestion
-
remove unsafe or unnecessary embedded elements
-
export a cleaner version for safer AI use
This is especially useful when documents come from external sources or move through shared workflows.
How It Works
Upload text or a PDF.
Scan for hidden prompts, invisible text, metadata risks, and suspicious instructions.
Review flagged findings with clear explanations.
Sanitize the content and export a cleaner version for safer AI use.
Core Protection Features
Hidden Prompt Detection
Find instructions that are visible to AI systems but easy for people to miss.
Invisible Text Scanning
Catch zero-width characters, hidden formatting, and obfuscated text patterns.
PDF Sanitization
Remove embedded risk from PDFs before they enter an AI pipeline.
Prompt Injection Defense
Reduce the chance that external content can manipulate model behavior or leak data.
What You Get
A safer way to review text before AI ingestion
Cleaner PDFs for summaries, drafting, and search
Better visibility into hidden instructions and risky formatting
More control over what your AI system is actually reading
A repeatable workflow for scanning and sanitizing uploaded content
Who This Is For
Students
Check essays, study materials, pasted research, and uploaded files for hidden instructions before using AI tools for summaries, drafting, or revision.
AI Product Teams
Protect assistants, agents, and document-ingestion workflows from unsafe file input.
Security and Compliance Teams
Review uploaded content before it reaches internal AI tools.
Operations Teams
Standardize a repeatable scan-and-sanitize workflow for everyday document handling.
Anyone Using AI With File Uploads
Add a safety layer before PDFs are summarized, searched, or processed.
Why This Matters for AI Safety
Prompt injection is not only a chatbot problem. It can arrive through external documents, copied text, and uploaded files that appear trustworthy at first glance.
When hidden instructions are allowed to pass directly into an AI workflow, the model may:
- follow unrelated commands
- expose information that was not requested
- shift away from the user’s real goal
- process hidden content as if it were valid instructions
That is why detection and sanitization need to happen before AI processing, not after.
FAQ
