Add Files to a Disc Later: Multisession in InfraRecorder

A multisession disc is written more than once: you burn some files today, leave the disc “open”, and add more files next week. InfraRecorder 0.53 can import session data from multisession discs and add further sessions, which makes it a practical tool for running backups and archives that grow over time. Multisession also has real traps — discs that appear to lose files, players that only see the first session, space silently consumed by session overheads — so this guide explains how sessions work, how to add files safely, and when to finally close the disc.

You need a disc that was started as multisession (or a blank disc for your first session), a burner, and InfraRecorder 0.53 from the download page. The program is free under GPL v3, built for Windows 2000 to Windows 7; it is not officially supported on Windows 10 or 11, though many users run it there — see InfraRecorder on Windows 11 for those notes. Note that adding sessions after the fact only works on media written with the session left open; a finalised disc cannot accept new sessions.

How Multisession Works

Each writing pass on a multisession disc is a session. Every new session carries its own table of contents, which — crucially — can point back at files recorded in earlier sessions as well as the new files just written. That is why the disc normally appears to hold everything at once: the latest session’s index lists the complete, current set of files. When you “delete” a file while preparing a later session, the file’s data is not erased from the disc (recordable media cannot erase) — it is simply dropped from the newest index, so it disappears from view. Earlier versions of a file you replaced remain physically present in their old sessions, hidden by the newer index entry. Two consequences matter. First, multisession is not a secure-deletion tool: sensitive files dropped from the index can still be recovered from the disc with the right tools. Second, every session costs overhead space for its lead-in, lead-out and index, so many small sessions waste noticeably more of the disc than a few large ones.

Step by Step: Adding Files to an Existing Disc

1. Insert the multisession disc in the burner — the same disc you started earlier, which was left unfinalised. Wait for the drive to read it.
2. Open InfraRecorder and start a data project in the usual way.
3. Import the previous session. Use the project’s option to import session data from the disc (InfraRecorder reads the last session’s index). This step is the heart of the process: importing tells the new project which files already exist on the disc, so they stay visible and only your additions are written. If you skip the import, the new session’s index will list only the new files, and the earlier files will appear to vanish — the classic multisession accident.
4. Confirm the existing files appear in the project listing, shown as already on the disc. If the listing is empty when you know the disc holds files, stop and re-import the session rather than continuing.
5. Add the new files to the project. You may also remove entries from the listing to hide files in the new index, remembering the warning above: hiding is not erasing.
6. Watch the capacity meter. The free space is what remains after all previous sessions and their overheads, not the disc’s original capacity. Version 0.53 adjusts the space meter automatically when a blank DVD is inserted; for a partly used multisession disc, trust the imported session’s accounting of what is left.
7. Decide: leave open or close. In the burn settings, leave the disc open for further sessions if you plan to add more later — or close/finalise it if this is the last addition. Closing writes the final lead-out and makes the disc readable in the widest range of drives; see the next section before choosing.
8. Burn the new session at a moderate write speed, with verification enabled where offered, and wait for completion without interrupting.
9. Eject, reinsert and check. Reinsert the disc and confirm the file listing shows old and new files together. This thirty-second check catches a missed session import while the lesson is still fresh.

When to Close the Disc

Leave the disc open only while you genuinely intend to add more. A disc left open can be awkward elsewhere: some older drives, standalone players and other operating systems read only the first session, or fail on unfinalised media altogether — which is why an unfinalised backup disc sometimes looks “empty” in another machine. When the disc is full, finished, or needed by someone else, close it. InfraRecorder can fixate/close discs by writing the lead-out, and on rewritable media the erase guide explains the related unclose option that reopens a finalised RW disc. For anything destined for an archive shelf or another person, a closed single-purpose disc — or a copy made with the disc-copy function — is the safer deliverable.

Risks and Good Habits

The recurring multisession failures are procedural, not mechanical: forgetting to import the previous session (files appear lost — they are not, but a later session written after that mistake complicates recovery); adding so many tiny sessions that overhead eats the disc; and trusting an open disc as a finished backup. Guard against all three with simple habits: always import and visually confirm the existing files before burning; batch additions into fewer, larger sessions; and treat the disc as a working copy until it is closed — at which point, verify it, label it with the closing date, and consider imaging it with the disc-to-ISO process so the finished archive also exists as a file. Finally, remember that a multisession disc’s newest index rules: back up or close important discs promptly rather than letting them live for months in the fragile open state.

Related Guides

New to burning generally? Start with burning an ISO file for single-shot image burns, and the ISO imaging guide for preserving finished discs as files. On rewritable media, multisession pairs naturally with the erase methods in erasing a CD-RW or DVD-RW — including erasing only the last session when an addition goes wrong.