Mozilla PDF.js vs ReadEra

Mozilla PDF.js is a free, web standards-based platform for parsing and rendering PDF files. Developers can use its display API to render documents and retrieve information, or adapt the viewer layer for a custom interface. That viewer is used in Firefox and project browser extensions. PDF.js renders annotations and supports adding a subset of annotation types, and it supports form filling; OCR is not provided. The project targets HTML5-compliant browsers and includes a legacy build for older browsers, although PDF feature support varies by browser and version. Prebuilt builds are available, with hosted copies listed through jsDelivr, cdnjs, and unpkg. Developers can clone and build it locally, but some browsers require a local web server instead of opening PDFs through file URLs. Cross-origin requests are blocked by default, so CORS or a server proxy may be needed. For large documents, rendering only visible pages can reduce memory use. PDF.js is licensed under Apache 2.0.

ReadEra is an app for reading books, magazines, articles, and documents without ads or registration. It opens formats including EPUB, MOBI, AZW3, FB2, PDF, DjVu, DOC, DOCX, RTF, ODT, TXT, CBR, and CBZ, along with files inside ZIP or RAR archives. The app detects books and documents and organizes them through reading lists, author and series groups, collections, sorting, and folder tools. Readers can add bookmarks, quotes, notes, translations, dictionary lookups, and text selections. Controls include search, contents, page history, display modes, and settings for fonts, margins, hyphenation, zoom, brightness, and rotation. Multiple books or documents can be read at once, including in split-screen. Kids mode offers a simplified interface, parental control, and child-specific filtering and collections. Premium syncs books, documents, progress, bookmarks, and quotes with Google Drive, and adds background text-to-speech. ReadEra is available on Android, iOS, and macOS. The free plan costs nothing; Premium costs $14.99, paid once.