qai ipi techniques to list them programmatically, or --format to filter by format.
PDF Techniques
PDF has the broadest technique coverage with 10 techniques split across two phases.Phase 1 — Basic Hiding
| Technique ID | Name | Description |
|---|---|---|
white_ink | White Ink | White text on white background — invisible to humans but extractable by PDF parsers |
off_canvas | Off Canvas | Text positioned at negative coordinates, outside the visible page area |
metadata | Metadata | Payload stored in PDF metadata fields (Author, Subject, Keywords) |
Phase 2 — Advanced Hiding
| Technique ID | Name | Description |
|---|---|---|
tiny_text | Tiny Text | 0.5pt font — below human visual threshold but parseable by text extraction |
white_rect | White Rectangle | Text drawn on the page then covered by an opaque white rectangle overlay |
form_field | Form Field | Hidden AcroForm text field with payload as the field value |
annotation | Annotation | Payload placed in the PDF annotation/comment layer |
javascript | JavaScript | Document-level JavaScript action with embedded payload |
embedded_file | Embedded File | Hidden file attachment stream within the PDF structure |
incremental | Incremental | Payload placed in a PDF incremental update section |
Image Techniques
3 techniques targeting vision-language models (VLMs) and OCR pipelines.| Technique ID | Name | Description |
|---|---|---|
visible_text | Visible Text | Human-readable text overlay on the image |
subtle_text | Subtle Text | Low contrast, small font, or edge-placed text — hard for humans to notice |
exif_metadata | EXIF Metadata | Payload stored in EXIF metadata fields |
Markdown Techniques
4 techniques targeting document processing pipelines that ingest Markdown.| Technique ID | Name | Description |
|---|---|---|
html_comment | HTML Comment | Payload in HTML comment tags (<!-- -->) — invisible when rendered |
link_reference | Link Reference | Payload in an unused link reference definition at the bottom of the file |
zero_width | Zero-Width | Payload encoded using zero-width Unicode characters (invisible in rendered output) |
hidden_block | Hidden Block | Payload in an HTML div with display:none — hidden when rendered in browsers |
HTML Techniques
4 techniques targeting web content and HTML document processing.| Technique ID | Name | Description |
|---|---|---|
script_comment | Script Comment | Payload in a JavaScript comment inside a <script> tag |
css_offscreen | CSS Off-Screen | Payload in an element positioned off-screen using CSS |
data_attribute | Data Attribute | Payload in an HTML data-* attribute |
meta_tag | Meta Tag | Payload in an HTML <meta> tag content attribute |
DOCX Techniques
6 techniques targeting Microsoft Word document processing.| Technique ID | Name | Description |
|---|---|---|
docx_hidden_text | Hidden Text | Text with the Word hidden font attribute — invisible in normal view |
docx_tiny_text | Tiny Text | 0.5pt font — below human visual threshold |
docx_white_text | White Text | White text on white background |
docx_comment | Comment | Payload in a Word comment/annotation |
docx_metadata | Metadata | Payload in document core properties (author, subject, etc.) |
docx_header_footer | Header/Footer | Payload in the document header or footer |
ICS Techniques
4 techniques targeting calendar invite processing (iCalendar format).| Technique ID | Name | Description |
|---|---|---|
ics_description | Description | Payload in the event DESCRIPTION property |
ics_location | Location | Payload in the event LOCATION property |
ics_valarm | VALARM | Payload in the VALARM reminder DESCRIPTION |
ics_x_property | X-Property | Payload in a custom X- extension property |
EML Techniques
3 techniques targeting email processing pipelines.| Technique ID | Name | Description |
|---|---|---|
eml_x_header | X-Header | Payload in a custom X- email header |
eml_html_hidden | HTML Hidden | Payload in a hidden HTML div (display:none) within the email body |
eml_attachment | Attachment | Payload in a text file attachment |
Technique Summary by Format
| Format | Technique Count | Technique IDs |
|---|---|---|
| 10 | white_ink, off_canvas, metadata, tiny_text, white_rect, form_field, annotation, javascript, embedded_file, incremental | |
| Image | 3 | visible_text, subtle_text, exif_metadata |
| Markdown | 4 | html_comment, link_reference, zero_width, hidden_block |
| HTML | 4 | script_comment, css_offscreen, data_attribute, meta_tag |
| DOCX | 6 | docx_hidden_text, docx_tiny_text, docx_white_text, docx_comment, docx_metadata, docx_header_footer |
| ICS | 4 | ics_description, ics_location, ics_valarm, ics_x_property |
| EML | 3 | eml_x_header, eml_html_hidden, eml_attachment |
| Total | 34 |