PDF Object Explorer Online — Inspect COS Dictionaries & Decoded Streams
Browse internal PDF COS object trees, trailer dictionaries, and decompressed FlateDecode streams online for free. In-browser alternative to iText RUPS.
DROP PDF FILES HERE
or browse your device to inspect internal COS trees, dictionaries, and byte streams
How PDF Object Explorer Works
Follow three direct steps to parse indirect objects, dereference pointers, and decompress binary streams in memory.
Queue Target Document
Select or drag your PDF file into the dropzone. The in-browser WebAssembly parser maps the trailer and cross-reference table in RAM.
Traverse Object Hierarchy
Browse catalog roots, page tree nodes, font descriptors, and resource dictionaries. Follow indirect references (e.g. 14 0 R) bidirectionally.
Decompress & Export Streams
Decompress zlib FlateDecode streams, inspect raw bytes in dual-pane hex dumps, and export raw binaries to your workstation.
Four Low-Level Object Exploration Modes
Low-level Carousel Object System inspection and real-time stream decoding built for security auditors, prepress operators, and software engineers.
COS Indirect Objects
Traverse indirect object graphs linking object IDs, generation numbers, and byte offsets. Follow indirect pointers recursively across complex document trees.
FlateDecode Engine
Decompress zlib-compressed binary streams in real time. Inspect uncompressed PostScript operators, vector paths, page description code, and embedded font headers.
Trailer & Catalog Parser
Parse /Root catalog, /Pages trees, /Outlines bookmarks, /AcroForm interactive fields, and /Info document dictionaries down to individual name-value keys.
Dual-Pane Hex Dumps
Inspect raw byte offsets with synchronized hexadecimal and ASCII columns. Copy stream fragments, verify binary headers, and audit byte positions.
Utilvo In-Browser vs Cloud Object Viewers
Why client-side in-memory COS inspection delivers deeper visibility, instant decompresion, and absolute privacy.
| Feature | Utilvo In-Browser | Cloud Object Viewers |
|---|---|---|
| COS Graph Traversal | Recursive bidirectional pointer dereferencing in local memory | Flat, non-navigable textual dumps with no pointer traversal |
| Stream Decompression Speed | Instant client-side WebAssembly zlib FlateDecode execution | Slow server-side round-trips with throttling and rate limits |
| Binary Hex/ASCII Inspection | Interactive dual-pane hex dump viewer with offset navigation | Truncated plain-text previews with non-printable byte loss |
| Confidentiality & Compliance | Zero bytes leave browser RAM (100% HIPAA/GDPR safe) | Entire proprietary PDF uploaded and stored on remote cloud disks |
| Object Export Capabilities | Instant client-side export of individual decompressed stream buffers | Restricted downloads or locked behind paid subscription tiers |
Navigating Indirect Objects, Generation Numbers & FlateDecode Streams
How our WebAssembly parser parses byte offsets, builds COS graphs, and safely decodes compressed binary streams.
Trailer Resolution & XRef Offsets
The parser locates the %%EOF marker at the end of the file and reads the startxref byte offset backwards. It reconstructs the object address map from traditional tables or compressed PDF 1.5 cross-reference streams.
Indirect Reference Dereferencing
Indirect references (objNum genNum R) are dereferenced lazily. The engine tracks visited object keys in a directed acyclic graph, preventing infinite circular reference loops in malformed or corrupted documents.
FlateDecode Inflate Mechanics
Stream objects carry length, filter, and decode parameters in their dictionary header. Compressed bytes are passed directly into a compiled WebAssembly inflate routine, yielding the raw uncompressed content stream.
Memory Sandboxing & Zero Leakage
All buffer allocations live inside the transient browser tab memory sandbox. No telemetry, dictionary tokens, or decompressed stream data are transmitted across the network, ensuring complete confidentiality.
Debugging PDF Syntax Errors & Stream Filters at the Object Level
Follow these recommended checks before auditing structural dictionaries and binary content streams.
Confirm File Integrity
Ensure the PDF contains a valid %%EOF marker so the parser can locate the startxref address offset accurately.
Check Encryption State
If the document has an /Encrypt dictionary, ensure valid user credentials are provided to inspect encrypted object streams.
Verify Filter Support
Verify that content streams use standard FlateDecode, ASCIIHexDecode, or ASCII85Decode compression algorithms.
Monitor Browser Memory
When exploring documents with thousands of objects, ensure sufficient workstation RAM is available for in-memory graph trees.
COS Object Types vs Specification Standards
Understanding how fundamental COS data types compare across ISO 32000 specifications.
| COS Object Type | Standard | Data Structure | Encoding / Compression | Role | Best Use Case |
|---|---|---|---|---|---|
| Unprocessed PDF Stream | ISO 32000-1/2 | Raw binary stream byte array | Binary file buffer | Source of this tool | Low-level structural debugging, malware analysis, forensic recovery |
| Decompressed Object Dump | RFC 1951 / zlib | Uncompressed PostScript operators | Plain text / byte array | Target of this export | Page description analysis, font extracting, forensic text recovery |
| Indirect Dictionary | ISO 32000-1 §7.3.7 | Key-value name-object pairs | COS Dictionary structure | Node descriptor | Page trees, font descriptors, catalog roots, metadata streams |
| COS Array Object | ISO 32000-1 §7.3.6 | Ordered sequence of objects | 1D sequential list | Container structure | Bounding boxes (/MediaBox), color palettes, font widths arrays |
| Indirect Reference (R) | ISO 32000-1 §7.3.10 | Object ID + Gen Number pointer | Graph edge reference | Linkage pointer | Connecting pages to resources, parent-child tree inheritance |
| FlateDecode Stream | RFC 1950 / zlib | Compressed payload + dictionary | Binary zlib payload | Content container | Page vector drawing commands, embedded fonts, high-res raster images |
Frequently Asked Questions
Understand how client-side COS object tree traversal parses indirect objects, decodes zlib streams, and audits byte offsets in local memory.
1What can developers inspect using the PDF Object Explorer?
Developers can traverse the entire indirect COS object tree (catalog dictionaries, page nodes, content streams, font descriptors, resources, and trailer dictionaries) directly in their browser.
2What are indirect objects and references inside a PDF?
PDF documents are structured as a graph of indirect objects (dictionaries, streams, arrays). Each object is uniquely indexed with an object and generation number (such as 12 0 R).
3Can I decompress and preview raw stream data?
Yes. The explorer attempts in-browser zlib FlateDecode decompression to preview raw PostScript content streams, embedded image frames, font files, and hexadecimal byte dumps.
4Are my proprietary code and PDF structures kept private?
Yes. All file parsing, indirect reference traversal, and stream decodings execute 100% locally in your browser memory via Web APIs with zero server uploads.
5What does the PDF Catalog /Root dictionary contain?
The Catalog dictionary represents the top of the object hierarchy, pointing to the Pages tree root, outline bookmarks, metadata streams, interactive AcroForms, and structure trees.
6Can I inspect hexadecimal byte offsets and download individual object streams?
Yes. You can switch to the dual-pane hex dump view with byte offsets and ASCII mapping, or download decompressed raw stream binaries with one click.
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