RenameNinja

RenameNinja is a native macOS application for batch renaming files by combining regular expressions to extract fields from original filenames and custom JavaScript code to transform those fields. The tool automatically extracts advanced metadata from images, audio files, videos, PDF documents, and Office files, making a wide range of variables available for use in renaming logic. The application offers an unlimited trial period with no functional restrictions, requiring a license only to remove periodic reminders. It is built entirely with SwiftUI and AppKit, ensuring deep integration with macOS starting from version Sonoma (14).

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• Field extraction using regular expressions. The user defines a regular expression pattern applied to each file's original name. Each capture group defined in the regular expression becomes an independent field that can be referenced later. This mechanism allows structured filenames (such as those containing dates, serial numbers, or identifiers) to be broken down into logical components that serve as the foundation for constructing the new name. If the regular expression does not match any file, the rename operation is blocked to prevent inconsistent results.
• Field transformation with custom JavaScript. For each file, the application executes a JavaScript code block defined by the user. Within this environment, the fields object provides access to all previously extracted fields as well as file metadata. The developer can modify, concatenate, or dynamically generate new values. A context object persists throughout the entire renaming process, allowing custom counters or shared states to be maintained across files, facilitating complex numbering sequences or non-linear logic.
• Final name construction using templates. Once fields have been processed with JavaScript, the user specifies a result pattern where fixed text can be interspersed with field references (such as {date}, {name}). The order and structure of the final name can be freely defined, enabling standardized naming conventions and the direct embedding of metadata such as image dimensions, EXIF data, or audio track information into filenames.
• Undo rename operations. The application maintains a record of the executed rename operation, allowing the change to be completely reversed using the undo function. This feature ensures that any transformation applied to files can be reverted without data loss, restoring filenames to their original state prior to the operation.
• Metadata extraction from images (EXIF). For image files, the software automatically reads EXIF metadata and exposes it as accessible fields. Available data includes dimensions (width and height in pixels), camera make and model, lens used, exposure time in decimal or fractional format, aperture, f-number value, ISO sensitivity, focal length, GPS coordinates (latitude, longitude, and altitude), and the original capture date and time. These fields can be used directly in JavaScript code or in the final template.
• Metadata extraction from video files. Video files provide technical metadata essential for editing or cataloging workflows. RenameNinja extracts duration in seconds, pixel dimensions, frame rate in frames per second (fps), resolution categorized into classes (8K, 4K, 1080p, 720p, 480p, or SD), number of audio tracks, and the creation date and time of the file. All this information is available as fields that can be incorporated into the renaming logic.
• Metadata extraction from audio files. For audio files, the application obtains data such as duration, track title, artist, album, genre, track number, disc number, release year, sample rate, bit depth, channel count, and channel configuration type (mono, stereo, or multi-channel). These metadata fields allow music libraries or sound files to be organized with precise criteria based on the intrinsic content of each file.
• Metadata extraction from PDF documents. PDF files provide a set of fields including title, author, subject, creator, producer, creation date and time, modification date and time, and total page count. This functionality proves useful for managing large volumes of documents, allowing structural information from the PDF to be incorporated directly into the filename without opening each document manually.
• Metadata extraction from Office documents. Microsoft Office files (Word, Excel, PowerPoint) and iWork files (Pages, Numbers, Keynote) expose metadata through the macOS Spotlight system. Available fields include title, authors, creator, description, and subject of the document. Although the availability of this data depends on the information embedded in each file, its integration enables renaming workflows based on document content.
• Real-time preview and field highlighting. The main interface displays a table with all loaded files, their original names, and the computed new names based on the defined rules. Each extracted or generated field is visually highlighted, and fields unavailable for a specific file are marked in red, providing immediate feedback on potential inconsistencies. A tree view panel allows exploration of all available metadata per file in real time.
• Saving recent sessions and quick access. The application automatically stores the last ten rename sessions, including the regular expressions, JavaScript code, and templates used. Through the recent sessions menu, the user can retrieve previous configurations without redefining the transformation logic, streamlining repetitive or similar tasks.
• Validation before renaming. The rename button remains disabled until all files in the list successfully pass the extraction stage using the regular expression and the execution of the JavaScript code. This validation prevents incomplete operations or partial errors that could leave files inconsistently renamed, ensuring that the defined rule applies to the entire set of selected items.
• QuickLook preview of original files. Double-clicking any filename in the list activates the system QuickLook function, displaying a preview of the original content without opening the associated application. This feature facilitates content verification before applying the rename operation, particularly when working with multimedia files or documents.

The RenameNinja application was created by an independent developer under the Loshadki brand, with the goal of providing a renaming tool based on precise software engineering principles, oriented toward users with technical expertise who require complete control over filename transformation. Development began in 2023, and the first public version was released with support for macOS Sonoma. The program is written entirely in Swift, utilizing SwiftUI for the user interface and AppKit for deep integration with the macOS file system and metadata services. The core renaming logic employs Swift's native regular expression engine and the JavaScriptCore framework, which enables JavaScript code execution in an isolated and secure manner within the application environment.

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