TIFF (Tagged Image File Format, .tiff, .tif)

Tagged Image File Format (abbreviated TIFF) is a file format for storing images, including photographs and line art. It is now under the control of Adobe. Originally created by the company Aldus for use with what was then called "desktop publishing", the TIFF format is widely supported by image-manipulation applications, by publishing and page layout applications, by scanning, faxing, word processing, optical character recognition and other applications. Adobe Systems, which acquired Aldus, now holds the copyright to the TIFF specification. TIFF has not had a major update since 1992, though several Aldus/Adobe technical notes have been published with minor extensions to the format, and several specifications, including TIFF/EP, have been based on the TIFF 6.0 specification.

TIFF is a flexible and adaptable file format. It can handle multiple images and data in a single file through the inclusion of "tags" in the file header. Tags can indicate the basic geometry of the image, such as its size, or define how the image data is arranged and whether various image compression options are used. For example, TIFF can be used as a container for JPEG and RLE (run-length encoding) compressed images. A TIFF file can also include a vector-based Clipping path (an outline that crops or frames the main image). The ability to store image data in a lossless format makes TIFF files a useful method for archiving images. Unlike standard JPEG, TIFF files using lossless compression (or no compression at all) can be edited and resaved without suffering a compression loss. Other TIFF file options include multiple layers or pages.

Although it is a widely accepted standard format today, when TIFF was first introduced, its extensibility led to compatibility problems. Programmers were free to specify new tags and options, but not all programs implemented support for all the tags that had been created. As a result the lowest common denominator soon became TIFF, and even today the vast majority of TIFF files, and the code that reads them, are based on a 32-bit CMYK or 24-bit RGB uncompressed image.

TIFF has an option to use LZW compression, a lossless data compression technique for reducing file size. Until 2004, the use of this option was limited because the LZW technique was the subject of several patents. However, these patents have now all expired.

Every TIFF file begins with a 2-byte indicator of byte order: "II" for little endian and "MM" for big endian byte ordering. The following 2 bytes represent the number 42. The number 42 was selected "for its deep philosophical significance." The reading of 42 is dependent on the byte order indicated in the first 2 bytes. All words, double words, and so on, in the TIFF file are read based on the indicated byte order.

The TIFF 6.0 Specification (Section 7: Additional baseline TIFF Requirements) states that compliant TIFF readers must support both byte orders. However, TIFF writers are free to choose whichever byte order is most convenient.