Mainframe Tools
EBCDIC Viewer
Open any mainframe EBCDIC file and instantly see its records, hex data, and field layout.
Open any mainframe EBCDIC file and instantly see its records, hex data, and field layout.
Click + Open next to Data Files in the sidebar. Pick any .dat, .bin, or raw mainframe file.
Click + Open next to Copybooks. Pick the matching .cpy or .cob file. The app parses it and auto-binds it to your data file.
Use the ◀ ▶ arrows in the toolbar to step through records one by one. Each record shows its decoded field values on the left and raw hex bytes on the right.
Title bar — shows the active data file and copybook. The VB/FB pill switches between Variable-Blocked and Fixed-Blocked record formats. Records / Raw file toggles the view mode.
Sidebar — lists all open files and loaded copybooks. Click a copybook to bind it to the selected file. Hover a file to reveal the × close button.
Record layout pane — one row per COBOL field. Shows byte offset, length, field name, and decoded value for the current record. Click a row to highlight it in the hex view.
Hex pane — raw bytes of the current record. Highlighted bytes correspond to the selected field. Click any byte to jump to its field.
Switch between Variable-Blocked (each record has a 4-byte length prefix) and Fixed-Blocked (all records are the same length). The app auto-detects this on open — only flip it if records look misaligned.
Some copybooks define multiple layouts over the same bytes (e.g. a field that is either a string or a number depending on record type). Enable this to see all alternate field interpretations side by side, each colour-coded.
Records — navigate one record at a time with the ◀ ▶ arrows. Requires a copybook to be bound.
Raw file — shows the entire file decoded as EBCDIC text, one line per record. Useful for a quick visual scan.
Drag in any .cpy or .cob file. Handles nested groups, REDEFINES, OCCURS, COMP, COMP-3, and both fixed and free format.
Correctly decodes zoned decimal, packed decimal (COMP-3), and binary integers (COMP/BINARY) — not just text fields.
Toggle alternate field layouts for multi-segment files. Each branch gets its own colour so overlapping fields are easy to spot.
Automatically detects IBM Variable-Blocked format (standard and cobrix-style RDW headers) so record boundaries are always correct.
Switch themes, accent colour, bytes-per-row, and codepage (CP-037 / CP-1047) from the ⚙ settings menu.
Drag the divider between the record layout and hex panes. Drag column headers to resize individual columns.
brew tap ramkumarsun-group/tap brew install --cask ebcdic-viewer
No download dialogs, no quarantine warnings. Works on Apple Silicon and Intel Macs.
xattr -cr "/Applications/EBCDIC Viewer.app"xattr step removes macOS's quarantine flag for unsigned apps.