SharedStrings

SharedStrings is a concept often encountered in data formats, particularly those used for spreadsheets and document interchange, such as Microsoft's Open XML format (OOXML). The core idea behind SharedStrings is to optimize storage by avoiding redundant data. Instead of storing the same string value multiple times throughout a file, the string is stored once in a dedicated "shared strings" section. Each occurrence of that string in the document then refers back to its single entry in the shared strings table.

This approach significantly reduces the overall file size, especially for documents containing a large number of repeated textual elements. For example, in a spreadsheet with many cells containing the same header text or common labels, storing these labels only once in the shared strings table and then referencing them by index everywhere else is much more efficient than embedding the full text of the label in every single cell.

When a program reads a file that utilizes shared strings, it first parses the shared strings table to load all unique string values into memory. Then, as it encounters references to these strings within the main document content, it looks up the corresponding string value from the loaded table. This process of sharing common data is a fundamental optimization technique used in various data serialization formats to improve performance and reduce storage requirements.