Convert RAR to RAR Online (Rebuilding an Archive Under Different WinRAR Settings)

Rebuilding a RAR Archive Under a Different Format Version Is a Real Operation

A RAR archive isn't one fixed thing internally — RAR4 and RAR5 are genuinely different container formats sharing the same extension, and RAR5, the default since WinRAR 5.0 in 2013, changed real structural details underneath: its encryption moved from RAR4's AES-128 with a custom key-derivation approach to AES-256 with keys generated through PBKDF2-SHA256 run 131,072 times, its recovery-record structure dropped RAR4's 512-byte sector layout in favor of a percent-of-archive-size design with no fixed cap, and its volume-splitting scheme abandoned the older .r00-style extension naming entirely in favor of .part001.rar-style names. Rebuilding an old RAR4 archive as RAR5, or the reverse for compatibility with older software, means fully decompressing the original archive and re-encoding it under the other format's rules — nothing about that process is symbolic or unnecessary; the two containers are structurally different documents.

The same logic applies to several other RAR-to-RAR changes that have nothing to do with format version at all: adding a recovery record to an archive that didn't originally have one, removing one to save space, changing or adding a password, switching solid compression on or off, or re-splitting a single archive into a different number or size of volumes. Every one of these requires WinRAR to touch the archive's actual compressed data or header structure, which is exactly what a rebuild does.

Why a Recovery Record Can't Just Be Added to an Existing Archive in Place

RAR5's recovery record is built from Reed-Solomon error-correction codes generated over the archive's actual compressed bytes, sized as a chosen percentage of the archive that can reach up to matching the archive's own size. Because that record is mathematically derived from the specific data already inside the archive, adding one to a RAR that didn't originally include it means WinRAR has to process the whole archive again to generate the correction data — it isn't a simple metadata flag that gets flipped on. The same is true in reverse: stripping an existing recovery record back out to save space also means rebuilding the archive's structure without that section, rather than just deleting a marked chunk of bytes.

Password changes work similarly for a related reason: RAR5 encryption derives its AES-256 key from the password itself through PBKDF2-SHA256, and that derived key is what the compressed data is actually encrypted with. Changing the password means the data has to be decrypted with the old derived key and re-encrypted with a newly derived one — there's no way to swap just the password field and leave the underlying encrypted bytes untouched, since those bytes are mathematically tied to the specific password that produced them.

What Re-Archiving a RAR as a RAR Can Change and What Stays Fixed

• Gain — compatibility with older RAR-reading software: rebuilding a RAR5 archive as RAR4 lets it open on tools or embedded devices built before the 2013 format switch.
• Gain — stronger encryption: rebuilding a RAR4 archive as RAR5 upgrades AES-128 with a weaker key derivation to AES-256 with PBKDF2-SHA256 at 131,072 rounds — but only if the original password is known, since the archive must be decrypted first.
• Gain or lose — a recovery record: adding one trades some archive size for the ability to repair certain kinds of physical damage later; removing one reclaims that space.
• Gain or lose size — solid mode toggled: turning solid compression on usually shrinks a batch of many similar files further, at the cost of slower single-file extraction later.
• Gain — a different volume split: re-splitting into more, fewer, or differently sized volumes accommodates a new email attachment limit or upload cap without changing the actual content.
• Lose — nothing about the underlying files: a rebuild changes the container's format version, encryption, recovery data, and volume layout, never the extracted files' own bytes.

Which WinRAR Settings Actually Control Each of These Rebuild Options

WinRAR's archive-creation dialog exposes the RAR4-versus-RAR5 format choice directly as an "Archive format" option, letting an existing archive be extracted and rebuilt under either version explicitly. The recovery record is added through the same dialog's "Recovery record" setting (or the standalone RR command in the command-line rar tool), specified as a percentage of the archive rather than a fixed byte count under RAR5. Splitting into volumes is controlled by the "Split to volumes" size field, and WinRAR's own naming behavior switches automatically between the .part001.rar scheme (the default since version 3.0) and the older .r00-style extension scheme only for RAR4 archives, since RAR5 doesn't support the older naming at all.

Because RARLAB's unRAR code is licensed for extraction only, every one of these rebuild operations has to run through WinRAR or RARLAB's own rar.exe specifically — the same restriction that applies to creating a RAR from any other source format applies just as fully here, since rebuilding still counts as creating a new RAR archive from the software's own compression engine, not merely reading an existing one.

WinRAR's command-line rar tool also supports these same rebuild operations as scriptable flags rather than dialog clicks — options like -rr[N] for a recovery record percentage, -hp for password-protecting both data and filenames, and -v for volume size all apply during archive creation, meaning an automated backup script can rebuild a RAR under new settings as one step in a larger pipeline instead of requiring someone to manually work through WinRAR's graphical interface each time.

Real Situations That Send People Back to Re-Archive an Existing RAR

A well-documented pattern involves a RAR5 archive failing to open on older RAR-reading software or an embedded device built before the 2013 format switch, reporting the file as unreadable even though nothing is actually damaged — rebuilding the same archive specifically as RAR4 through WinRAR's format option is the documented fix, since RAR4 remains readable by that older software while RAR5 simply isn't recognized.

A second real scenario involves archives originally created without a recovery record that are then moved to long-term storage on unreliable media, where a later request to add recovery protection means the whole archive has to pass back through WinRAR once to generate the Reed-Solomon data, since it can't be appended without touching the existing compressed structure.

A third scenario shows up around shared archives whose password needs to change after a team member with access leaves a project — since RAR5's encryption key is derived directly from the password via PBKDF2-SHA256, there's no way to rotate the password without decrypting the archive with the old one and re-encrypting it with the new one, making a full rebuild the only way to actually retire the old credential.

A fourth pattern involves an archive originally split for one specific size limit, such as an older email provider's attachment cap, that later needs re-splitting for a different constraint entirely, like a smaller upload ceiling on a new file-sharing service — since the volume boundaries are baked into how the compressed data itself is divided across files, hitting a new size limit means rebuilding the split from scratch rather than simply re-labeling or re-cutting the existing volume files.

Common RAR-to-RAR Rebuild Scenarios Side by Side

Questions About Rebuilding an Already-RAR Archive

Why would I convert a RAR to another RAR instead of leaving it alone?
Because the file staying a RAR doesn't mean everything inside it stays the same — the format version, encryption strength, recovery record, solid-compression setting, and volume split can all change while the extension stays identical.

Can I add a recovery record to a RAR archive without rebuilding it?
No. RAR5's recovery record is generated from Reed-Solomon codes computed over the archive's actual compressed data, so adding one means WinRAR has to process the whole archive again, not just append a separate section.

Can I change a RAR archive's password without knowing the original one?
No. The archive has to be decrypted with the current password before a new one can be applied, since RAR5's encryption key is derived directly from whichever password produced the existing encrypted data.

Why would I rebuild a RAR5 archive as RAR4?
For compatibility with RAR-reading software or embedded devices built before 2013, which sometimes can't parse the newer RAR5 container at all and report the archive as unreadable.

Does re-splitting a RAR into different volume sizes change the files inside it?
No. Changing how an archive is split across volumes only affects the container's layout on disk — the extracted files themselves come out identical regardless of how many volumes the archive was divided into.