An ECSBX file is an archive saved in the Error-Correcting SeqBox Container format (ECSBX). It is created by blockyarchive, which is a utility used to create, rescue, and handle archives of system files in case of corrupted or loss of data. ECSBX files are similar to .SBX SeqBox (Sequenced Box) archives but include error-correcting capabilities not available in the SBX format.

The ECSBX file format stores information in a collection of blocks with each block consisting of a header, unique file identifier, checksum, block sequence number, and version. It is based on the SeqBox format, which is designed to provide a safe archiving solution for securing and storing user's files. The difference between the formats is that the ECSBX format error correction via Reed-Solomon erasure code.