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John the Ripper is a command-line tool for authorized password auditing and recovery. Openwall describes its primary purpose as detecting weak Unix passwords; community-enhanced “jumbo” builds can handle many additional hash and encrypted-file formats. Which formats work depends on the particular build and correctly prepared input.
What is John the Ripper used for?
John the Ripper (often shortened to John or JtR) tests candidate passwords against password hashes and, in some builds, supported encrypted-file data. Its intended role is broader than intrusion: system administrators and security teams can use it to identify weak passwords in data they are authorized to audit, while users may use it for legitimate recovery.
The standard version supports a range of Unix password hash types, Kerberos/AFS, Windows LM hashes, and DES-based tripcodes. Openwall says jumbo versions add hundreds of hash and cipher types, including examples such as Windows NTLM, macOS, web applications, database servers, SSH private keys, encrypted archives, and protected documents. These are examples of jumbo coverage, not a guarantee that every binary supports every format. See the Openwall overview.
A hash is a one-way representation that John tests candidate passwords against. Encrypted files are different: a compatible jumbo build may test supported encrypted material, but the file often needs to be converted into a format John can process. A file extension alone does not establish that the selected build can handle it.
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How John generates password candidates
John offers several approaches for producing candidates. Choose based on the authorized audit or recovery task and the information available; none guarantees a recovery.
| Mode | How it generates candidates | When it may fit |
|---|---|---|
| Single crack | Uses account-associated information, such as login names and name fields, to generate candidates for corresponding accounts, together with rules. | A sensible starting point for a password file containing account information; Openwall recommends starting here. |
| Wordlist | Tests entries from a text wordlist. Optional rules transform words into additional candidates; list order affects which entries are tried first. | When you have an appropriate wordlist and want to try its candidates, optionally with rule-based variations. |
| Incremental | Generates combinations from configured character sets and length parameters. | When configured candidate generation is appropriate and you can account for potentially extensive computation. A broad run may not finish in useful time. |
| External | Uses a custom candidate-generation mode defined in a configuration section with a subset of C. | Specialized cases where an operator needs to define candidate generation. |
Openwall documents these approaches in its cracking modes guide and explains wordlist configuration in its configuration documentation. The outcome depends on the target hash or cipher, candidate choices, configuration, available time and resources, and whether the input is recognized correctly. Openwall’s reviewed documentation does not provide a general success rate or a current benchmark that applies across formats.
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How to start a run, view results, and resume
The commands below follow Openwall’s documented examples. Use only a password file or converted input you are authorized to assess; the sample filename is illustrative, not a real target.
- Run a basic check: use
john passwd, replacingpasswdwith the path to your prepared, authorized input file. John selects an approach based on its normal workflow. - Choose wordlist mode when appropriate: run
john --wordlist=/path/to/wordlist --rules passwd. Replace both paths with your own input and wordlist. Rules add transformed candidates from the listed words. - Display recovered results: run
john --show passwdagainst the same input file to display passwords John has recovered. - Resume an interrupted session: run
john --restore. John saves session state periodically, allowing a run to continue rather than start over.
Recovered passwords are also stored in john.pot. The pot file lets John avoid reloading hashes it has already cracked in a later run. Keep it protected: it contains recovered credentials. Openwall’s overview describes basic usage and session handling; its usage examples provide further workflows.
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- POWERFUL SECURITY KEY: The YubiKey 5 NFC is the most versatile physical passkey, protecting your digital life from phishing attacks. It ensures only you can access your accounts
- WORKS WITH 1000+ ACCOUNTS: Compatible with popular accounts like Google, Microsoft, and Apple. A single YubiKey 5 NFC secures 100+ of your favorite accounts, including email, password managers, and more
- FAST & CONVENIENT LOGIN: Plug in your YubiKey 5 NFC via USB and tap it, or tap it against your phone (NFC), to authenticate. No batteries, no internet connection, and no extra fees required
- MOST SECURE PASSKEY: Supports FIDO2/WebAuthn, FIDO U2F, Yubico OTP, OATH-TOTP/HOTP, Smart card (PIV), and OpenPGP. That means it’s versatile, working almost anywhere you need it
- PRIMARY & SPARE KEYS: Just like having a spare house key, we recommend buying two YubiKeys - one for daily use and one as a spare. That way you’ll never get locked out of your accounts
Why does John say “No password hashes loaded”?
That message means John did not load usable hashes from the supplied input. It does not, by itself, mean the passwords are uncrackable. Check the input preparation, the selected build, and the format John is trying to recognize.
- Confirm the input is prepared for John. Some encrypted files require a conversion utility before John can process them. Openwall lists utilities such as
ssh2john,pdf2john,rar2john, andzip2johnfor certain file types in its FAQ. - Check that the build supports the format. Some types are available only in jumbo builds, and jumbo binaries do not all necessarily include the same features. A mode change cannot add support for a missing format.
- Consider ambiguity in the encoding. Similar-looking hash strings can represent different formats. Openwall gives a 32-character hexadecimal string as an example of an encoding that may be ambiguous. Use reliable context to identify the type, then specify it with
--formatif needed; do not guess based on appearance alone. The command-line options and FAQ explain format selection.
Builds and performance: what to check
“Jumbo” describes a family of community-enhanced builds, not a single feature-complete executable. Before choosing a build, verify that it supports the required hash or cipher format and includes any needed input-preparation utilities. Openwall’s overview and FAQ describe format and build caveats.
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- POWERFUL SECURITY KEY: The Security Key NFC is the essential physical passkey for protecting your digital life from phishing attacks. It ensures only you can access your accounts.
- WORKS WITH 1000+ ACCOUNTS: Compatible with Google, Microsoft, and Apple. A single Security Key NFC secures 100 of your favorite accounts, including email, password managers, and more.
- FAST & CONVENIENT LOGIN: Plug in your Security Key NFC via USB-A and tap it, or tap it against your phone (NFC) to authenticate. No batteries, no internet connection, and no extra fees required.
- TRUSTED PASSKEY TECHNOLOGY: Uses the latest passkey standards (FIDO2/WebAuthn & FIDO U2F) but does not support One-Time Passwords. For complex needs, check out the YubiKey 5 Series.
- BUILT TO LAST: Made from tough, waterproof, and crush-resistant materials. Manufactured in Sweden and programmed in the USA with the highest security standards.
Parallel processing is also conditional. Openwall documents OpenMP support as dependent on build configuration and hash type: some binaries are compiled for multiple cores, and not every format supports it. Do not assume John will use all available cores or expect a particular speed without checking the selected build and target format.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is John the Ripper the right tool?
John is a fit when you need a command-line password-auditing or recovery tool and can supply input in a format supported by your build. Its modes provide different candidate-generation strategies, while its format coverage can extend substantially in jumbo builds. If you need a managed environment, Openwall describes a cloud bundle based on a pre-generated Amazon Machine Image at John the Ripper in the cloud; it is a cloud service, not a physical Amazon product. Openwall also offers a separate Pro product.
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