The Big Picture: More Than Just Web Pages
When you think of a search engine, you probably think of a tool that finds websites. But a search engine’s world is much bigger than that. A search engine’s crawlers are constantly discovering and indexing a wide variety of files, not just HTML pages. This is a key part of how a search engine organizes the internet.
Understanding what types of files a search engine can index is a crucial part of a smart SEO strategy. It helps you ensure that all of your valuable content, from a PDF to a video, has a chance to show up in search results.
The Core File Types a Search Engine Can Index
A search engine’s crawlers are designed to process many different kinds of file formats. Here are the main categories of files they can find and add to their index.
Document Formats
Many people don’t realize that a search engine can read and index a variety of document types. This is a huge opportunity for any business that publishes research, white papers, or guides.
- .pdf (Adobe Portable Document Format)
- .ps (PostScript)
- .csv (Comma-Separated Values)
- .epub (Electronic Publication)
- .kml / .kmz (Google Earth)
- .gpx (GPS eXchange Format)
- .hwp (Hancom Hanword)
- .rtf (Rich Text Format)
- .txt / .text (Plain text)
Web & Office Formats
A search engine’s crawlers are also very good at reading and understanding files created with common web and office software.
- .html / .htm (HTML)
- .xls / .xlsx (Excel)
- .ppt / .pptx (PowerPoint)
- .doc / .docx (Word)
- .odp (OpenOffice Presentation)
- .ods (OpenOffice Spreadsheet)
- .odt (OpenOffice Text)
- .svg (Scalable Vector Graphics)
- .tex (TeX / LaTeX)
Source Code Formats
For developers, it’s important to know that a search engine can also read and index source code files.
- .bas (Basic)
- .c / .cc / .cpp / .cxx / .h / .hpp (C / C++)
- .cs (C#)
- .java (Java)
- .pl (Perl)
- .py (Python)
Media Formats
The most engaging content is often not just text. A search engine can also find and index images and videos.
- Images: BMP, GIF, JPEG, PNG, WebP, SVG, AVIF
- Videos: 3GP, 3G2, ASF, AVI, DivX, M2V, M3U, M3U8, M4V, MKV, MOV, MP4, MPEG, OGV, QVT, RAM, RM, VOB, WebM, WMV, XAP
How to Optimize Non-HTML Files
Just because a search engine can find a file doesn’t mean it will automatically rank well. You need to optimize your files to give them the best chance of showing up in search results.
1. Use Descriptive Names
A file name should be a clear, descriptive summary of what the file is. For example, financial-report-2024.pdf is much better than doc1.pdf.
2. Optimize Your Media
Images and videos can have a huge impact on your pagespeed. You should always use high-quality, optimized media with descriptive alt text.
3. Use HTML to Your Advantage
You can use a simple HTML page to introduce a document or a video. This is a great way to provide context and to ensure that a search engine knows what the file is about.
