A comprehensive reference covering ISRC, ISWC, DDEX, and CWR standards — what they are, why they matter, and how to get them right.
Every year, billions of dollars in music royalties go unpaid or are misdirected — not because platforms refuse to pay, but because they can't match the asset to the rightsholder. The culprit is almost always fragmented, missing, or inconsistent metadata.
The music industry has developed four core standards to solve this problem. When used correctly, they create a shared language between rights holders, distributors, PROs, DSPs, and collection societies that lets money flow to the right people automatically. When ignored or misapplied, they create the kind of mess that takes years of dispute resolution to untangle.
This reference covers all four standards: what each one identifies, how to read its format, who issues it, and when you need it.
An ISRC identifies a specific recording — the master. Every unique recording of a song gets its own ISRC. A studio album version, a live version, and a radio edit of the same song are three different recordings and require three different ISRCs. If you re-record a track, the new recording gets a new ISRC even if the underlying composition is unchanged.
This is the identifier that DSPs (Spotify, Apple Music, Amazon Music, YouTube Music, etc.) use to track streams, match usage reports, and pay out neighboring rights and master royalties. Without a valid ISRC, your recording is essentially invisible to the royalty collection infrastructure.
CC-XXX-YY-NNNNN
| Segment | Length | Description |
|---------|--------|-------------|
| CC | 2 chars | Country code (ISO 3166-1 alpha-2) of the registrant |
| XXX | 3 chars | Registrant code assigned by the national ISRC agency |
| YY | 2 digits | Year of reference (last two digits) |
| NNNNN | 5 digits | Designation code — sequential number assigned by the registrant |
Example: US-S1Z-99-00001
US — registered by a US-based registrantS1Z — registrant code for that organization99 — year of reference: 199900001 — first recording registered by that registrant that yearWhen displayed, ISRCs are written with hyphens but stored and transmitted without them (USS1Z9900001). Be aware that some systems expect one format or the other — always confirm which a system accepts before bulk importing.
ISRCs are assigned by the recording's producer or rights holder — typically the record label or, for independent artists, the artist themselves. You don't submit an application for each individual ISRC. Instead, you obtain a registrant code from your national ISRC agency (in the US, that's RIAA; in the UK, PPL; in most other countries, the local phonographic rights body), and then you generate ISRCs yourself within that namespace.
Distributors often assign ISRCs on behalf of their clients if you don't already have them. This is convenient but means you may not own or control those codes — check your distributor agreement carefully.
When you create a recording asset in Resolut, you can enter an existing ISRC or request one through your connected registrant account. Resolut validates the format on input and flags duplicates across your catalog. If you're managing a large back catalog import, the CSV template includes an ISRC column — see the upload guide for format requirements.
An ISWC identifies a musical work — the composition, meaning the melody and lyrics as a creative work separate from any recording of it. Where an ISRC tracks a specific recording (the master), an ISWC tracks the underlying song itself. Every arrangement and recording of "Yesterday" by Lennon/McCartney shares a single ISWC; each individual recording has its own ISRC.
The ISWC is the primary identifier used by publishers, PROs (ASCAP, BMI, SESAC, PRS, SOCAN, etc.), and collection societies when registering works, claiming performance royalties, and resolving ownership disputes. It's the anchor that ties together multiple recordings, multiple publishers, and multiple territory registrations for the same composition.
T-NNNNNNNNN-C
| Segment | Description |
|---------|-------------|
| T | Literal prefix, always "T" (for "text/tune") |
| NNNNNNNNN | 9-digit work identifier assigned sequentially by CISAC |
| C | Single check digit (calculated using a standard algorithm) |
Example: T-034.524.680-1
Note that periods are used as visual separators in some representations but are not part of the code itself. The canonical form is T0345246801.
The distinction is fundamental to music rights:
A single ISWC can have thousands of ISRCs associated with it (every cover version, every live recording, every remix). The composition rights (tracked by ISWC) flow to the songwriter and publisher; the recording rights (tracked by ISRC) flow to the artist and label.
Unlike ISRCs, you don't self-assign ISRCs — they are assigned by CISAC (the international confederation of authors and composers societies) through your affiliated PRO or publisher administrator. The process:
If you're a songwriter without a publisher, you can register directly with your PRO (ASCAP, BMI, etc.), which will handle CISAC registration on your behalf. ISWCs are typically assigned within a few weeks of registration, though timing varies by society.
DDEX is not a code or identifier — it's a suite of XML-based messaging standards for exchanging music data between business partners in the digital supply chain. Where ISRCs and ISWCs are stamps you put on content, DDEX is the envelope and language you use to communicate about that content with DSPs, distributors, and data aggregators.
DDEX is maintained by the DDEX consortium, whose members include major labels, DSPs, distributors, and PROs. Compliance is effectively mandatory if you're delivering content to tier-1 DSPs at scale — Spotify, Apple Music, Amazon, and YouTube all accept (and often require) DDEX-formatted deliveries.
ERN — Electronic Release Notification
The most widely used DDEX message type. ERN is how a label or distributor tells a DSP "here is a new release, here is the content, here is the metadata." It includes:
Current standard: ERN 4.x (ERN 3.x is still in use at some legacy endpoints but ERN 4 is the current version for new integrations).
MEAD — Music Licensing, Education and Administration Data
Used for licensing data exchange between publishers, administrators, and licensees. Less commonly encountered in day-to-day distribution work, but important for complex sync and print licensing workflows.
DSR — Digital Sales Report
The format DSPs use to report usage back to rights holders and distributors. DSR messages contain:
Receiving DSR messages from DSPs requires a registered DDEX endpoint and processing infrastructure — most distributors absorb this and surface the data through their own dashboards.
RDR — Recording Data and Rights
Used to exchange recording-level rights information, including ISRC associations and rights holder splits at the recording level. More commonly used in neighboring rights administration than in standard distribution.
For most distribution use cases in 2025, you'll encounter:
If you're building a DDEX integration, always confirm the supported versions with your target endpoint before starting implementation.
CWR (Common Works Registration) is a standard file format developed by CISAC for registering musical works with PROs and collection societies. It's the mechanism publishers use to tell collecting societies around the world "this work exists, here are the writers, here are the publishers, and here are our ownership percentages."
Where DDEX handles the recording side of the supply chain, CWR handles the publishing side. If DDEX is how you get your master recordings into DSPs, CWR is how you get your compositions registered for performance and mechanical royalty collection.
A typical CWR workflow:
.cwr file (ASCII-based, fixed-width record format)A single CWR submission can register hundreds or thousands of works simultaneously. For publishers with active catalogs, CWR submissions happen on a regular cadence — often monthly or after each significant release.
CWR files are ASCII text files with fixed-width records. Each record type is identified by a two-character record type code:
| Record Type | Description |
|-------------|-------------|
| HDR | File header — sender and recipient info |
| GRH | Group header — groups related transactions |
| NWR / REV | New work registration or revision |
| SWR | Special work writer (co-writers) |
| SPU | Special publisher — publisher details for the work |
| OWR | Other writer not affiliated with a PRO |
| ALT | Alternate titles |
| PER | Performing artist |
| REC | Recording details (links ISWC to ISRC) |
| ORN | Origin (film/TV placement info) |
| GRT | Group trailer |
| TRL | File trailer |
The current version in wide use is CWR 2.2. CWR 3.0 is in rollout and introduces XML alongside the legacy fixed-width format, with improved Unicode support and more granular rights descriptions.
For publishers and administrators, CWR compliance is non-negotiable. Unregistered works don't collect. Mis-registered works collect to the wrong parties. Common CWR errors that cause royalty problems:
| Standard | What It Identifies | Format | Who Issues It | Primary Use Case |
|---|---|---|---|---|
| ISRC | A specific master recording | CC-XXX-YY-NNNNN (12 chars) | Registrant (label/artist) via national agency | DSP distribution, streaming royalties, neighboring rights |
| ISWC | A musical composition (work) | T-NNNNNNNNN-C (11 chars) | CISAC via your PRO or publisher administrator | Performance royalties, work registration, licensing |
| DDEX | Not an identifier — a messaging standard | XML messages (ERN, DSR, MEAD, RDR) | DDEX consortium maintains the spec | Digital delivery to DSPs, usage reporting, licensing data exchange |
| CWR | Not an identifier — a file/registration standard | Fixed-width ASCII (v2.2) or XML (v3.0) | CISAC maintains; submitted to PROs by publishers | Work registration with PROs and collection societies worldwide |
Resolut is built around these four standards as first-class data primitives:
ISRCs are assigned and tracked at the recording asset level. Resolut validates format on entry, detects duplicates across your catalog, and includes ISRC in all distribution exports. If you hold a registrant code, you can configure Resolut to auto-assign ISRCs from your namespace when creating new recordings.
ISWCs are tracked at the composition level within rights profiles. When you link a recording to a composition, Resolut carries the ISWC through to any downstream registrations and sync licensing documents. You can retrieve or update ISWCs as your PRO assigns them.
DDEX delivery is handled automatically when you connect a distribution integration. Resolut generates ERN-compliant packages using your asset metadata and sends them to connected DSP endpoints. DSR ingest for usage reporting is in active development.
CWR files can be exported from Resolut's publishing module for submission to your home PRO. The export validates shares, flags missing IPI numbers, and formats records to the CWR 2.2 specification. CWR 3.0 export is on the roadmap.
For questions about configuring any of these integrations, see the API and integration documentation or contact your account manager.
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