In computing, “master/slave” has been used for relationships such as a primary data store and its replicas, or a controller and subordinate processes. The labels can be imprecise, and standards bodies and software projects have increasingly favored terms that describe what a system actually does. There is no universal replacement: choose words that identify authority, copying, operating state, read/write roles, or coordination.
What “master/slave” describes in computing
The phrase has been applied to systems in which one component holds authority or original data while other components copy from it or act under its control. Khronos describes one common pattern as a single store of record with replicas that maintain copies of the original data. But the phrase has been used across different technical relationships, and the labels do not necessarily capture how every system behaves.
That lack of precision is one reason a direct word-for-word replacement can fail. A system’s “master” might be the writer, the active node, the source of copied data, or the controller. Those are related possibilities, not interchangeable descriptions.
Why standards bodies and projects are changing the terms
Organizations have cited both inclusion and clarity. INCITS said it would use inclusive terminology in new specifications, standards, documentation, and related materials, and asked that existing and legacy materials be updated where possible. It called for alternatives that better describe the technical capability or relationship. Phil Wennblom, then Senior Director of Standards Policy at Intel and chair of the INCITS working group on inclusive terminology, said: “Recognizing that language matters, the words we use to describe technology send messages that can bring people together or isolate and divide them.” INCITS announcement
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Migration also has practical costs. A terminology change may reach specifications, documentation, user interfaces, configuration, and code; legacy wording can persist where updates are difficult. In 2020, Jenkins described an incremental process that began addressing “slave” in 2016 and later included “master,” “blacklist,” and “whitelist.” The project chose “controller” for its former master role, and “allowlist” and “denylist” for the other terms, emphasizing that the right replacement depends on context. Jenkins terminology changes
The discussion has also involved compatibility and coordination: communities may settle on different terms, creating work when specifications, tools, or documentation need to align. IETF Internet-Drafts from 2020 discussed this concern, but they were drafts rather than binding standards. IETF draft on terminology
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Which replacement should you use?
Choose the pair that names the relationship you mean. Khronos and IETF guidance offer several options; none is a universal synonym for “master/slave.”
| What the relationship means | Possible terms | Use when |
|---|---|---|
| Authority or priority | primary/secondary | One component is authoritative or takes precedence over another. The June 2020 IETF draft notes primary/secondary as DNS terminology in RFC 8499. |
| Original data and copies | primary/replica | One store is the source and other stores maintain copies. |
| Operational state | active/standby | The distinction is whether a component is currently operating or waiting to take over. |
| Read and write roles | writer/reader | The relevant difference is which component writes data and which reads it. |
| Coordination and direction | coordinator/worker; controller/actor | One role coordinates or controls work performed by another. Confirm that the terms match the project’s actual architecture. |
| Leadership or hierarchy | leader/follower; parent/child; parent/helper | Use only when leadership or a parent-like relationship is what the system actually defines. |
The terminology appears in Khronos guidance and IETF drafts, which stress choosing the clearest pairing for the context. The August 2020 IETF draft particularly distinguishes authority (primary/secondary), originality (primary/replica), state (active/standby), and function (writer/reader). Khronos inclusive-language guidance · June 2020 IETF draft · August 2020 IETF draft
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A practical selection check
- Ask what the component does: hold the authoritative data, copy data, take an active or standby state, read, write, or coordinate.
- Name that behavior directly rather than preserving an old label by habit.
- Check that the new terms match the implementation and are understandable to the people who use the specification, interface, or code.
- When a short pair is misleading, use a longer description. Jenkins’ choice of “controller” is a project-specific example, not a universal replacement.
How widespread is the change?
Adoption is ongoing, not complete. A 2026 arXiv preprint analyzed 461 Linux Foundation repositories and reported an approximately 47% decline in non-inclusive terminology since 2020; it also found that 62.7% of those repositories still contained at least one Tier-1 non-inclusive identifier. The authors noted that much remaining terminology appeared outside source code, including in documentation, comments, configuration, and other artifacts. These figures describe that repository sample, not all software projects, and the paper is a preprint rather than a universal measurement. 2026 study of Linux Foundation repositories
A 2021 report on the public dispute surrounding standards work described changes then associated with MySQL, GitHub, Twitter, and W3C. Those are examples reported at that time, not evidence of each organization’s current policy. 2021 report republished by Linux.com
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Where did the term come from?
The technological origin is not established by the sources cited here. Khronos says the origins of “master/slave” in technology are unclear; the 2020 IETF drafts discuss terminology and alternatives but do not establish a first technical use. Treat any precise origin story or earliest-use claim as unverified unless supported by separate historical evidence. Khronos inclusive-language guidance
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