OneOpen: File Viewer

OneOpen is a multi-format file viewer for iPhone and iPad. Open documents, web pages, CAD drawings, 3D models and archives from Files, Mail and apps that support document sharing.

HTML and Markdown
Preview HTML, HTM and XHTML pages. Read Markdown / MD notes with headings, a table of contents, tables, code fences, task lists, footnotes and reference links. ZIP websites retain local images, styles and relative resources. Markdown in packages can display supported local images. Ordinary HTML allows restricted HTTPS/WSS networking by default, with offline and Safe Preview options. Markdown does not run scripts or load remote images.

CAD drawings and 3D models (Advanced)
• Pan, zoom and toggle layers in supported DWG/DXF 2D model-space drawings.
• Rotate STEP/STP, IGES/IGS, BREP/BRP, STL, OBJ and PLY models, including PLY vertex colors and point clouds.
• ZIP a complete OBJ model folder to load supported MTL materials, PNG/JPEG textures, normals, transparency and groups. A standalone OBJ shows geometry without reading private neighboring files.
• Preview supported static GLB / glTF 2.0 geometry, nodes, basic materials and PNG/JPEG textures. Model ZIPs retain relative resources. JSON and model information have separate views.
• USDZ starts in object view; choose AR when needed.
• Included models and engineering drawings demonstrate supported features.

Everyday viewing is free
Read PDF, Office/iWork, images, audio/video, JSON, XML, YAML, CSV, code and text. PDF supports continuous reading, zoom, search and page controls that hide while scrolling. Edit supported text in an independent working copy.

Archives and EPUB
Browse ZIP, 7Z, RAR, TAR, GZ, BZ2, XZ and supported TAR combinations. Open or share supported entries and save extracted files to Files. ZIP and EPUB remain free; other archive formats require Advanced Access.
EPUB follows the declared chapter order, with a table of contents, previous/next controls, current-chapter search and reading settings. Pages stay offline. A chapter error keeps navigation available. DRM, media overlays, annotations and whole-book search are unsupported.

Email, certificates and information
Decode EML headers, body text, common character encodings and attachment filenames. Open or share readable attachments independently. HTML email becomes text without loading remote content. Decryption, signature verification and TNEF extraction are not provided.
Inspect public CER, DER, CRT and PEM certificate subjects, issuers, validity, algorithms, public keys, usages and SHA-256 fingerprints. Certificates are never installed and device trust is not evaluated.
File Information includes PDF metadata, image/camera properties, media tracks, text encoding/line counts and archive summaries.

Open from other apps
Skippable onboarding uses real iOS screenshots to explain More, Edit and favorite ordering in the share sheet. Revisit it in Settings. Categories, Recents and widgets help you return to files.

Advanced Access and compatibil