Converting XLS files to XLSX format allows you to open, share, and use your content in applications that support XLSX but not XLS. XLS and XLSX differ in their internal data structure, compression method, and software ecosystem. The conversion process reads the binary or text content of the source XLS file, transforms the data into the XLSX encoding scheme, and writes the result as a new file. Where possible, metadata such as creation date, author, and embedded colour profiles is preserved in the output. Quality and fidelity depend on how closely the two formats share structural features — conversions between formats in the same category (e.g., two image formats or two document formats) generally preserve content more completely than cross-category conversions. 1converter processes XLS-to-XLSX conversions server-side: files are uploaded over HTTPS, converted on secure cloud infrastructure, and the output is ready to download within seconds. Converted files are automatically deleted after 24 hours.