ISO 18587 is the standard governing the post-editing of machine translation (MTPE): it defines who can review AI output, how that process should be organised, and what quality controls are required. ISO 17100 does the same for professional human translation. The essence of both is identical: qualified personnel, documented processes and auditable accountability. If you work with certified suppliers in other areas, it makes sense to demand the same from those who manage your multilingual communication.
What is ISO 17100 and which service does it cover
The ISO 17100:2015 is the specific international standard for professional translation services. It defines the minimum requirements an agency must meet: who is authorised to sign off as a translator, how the process must be organised from the moment the client submits the document until they receive the final delivery, and which quality controls are mandatory at each stage.
Specifically, the standard requires that each project undergoes two distinct phases: translation by a qualified professional and revision by a second independent linguist. Furthermore, it sets out the competence requirements for translators — a degree in translation or linguistics, or five years of documented professional experience in the sector.
At Overseas Translations, we have held ISO 9001:2015 and ISO 17100:2015 certification since 2017, both audited by Bureau Veritas. ISO 17100 covers all our professional human translation services: contracts, technical documentation, marketing materials, product sheets and corporate presentations.
What is ISO 18587 and which service does it cover
The ISO 18587 regulates something slightly different from the outset, although the underlying logic is the same. Here, the process does not begin with a blank text and a translator: it begins with the output of a machine translation engine — DeepL, Google Translate, or any other — which a human post-editor must review, correct and validate until the quality is comparable to that of a direct human translation.
The standard sets out the competencies the post-editor must demonstrate, the workflow and the applicable quality requirements. The post-editor’s profile is equivalent to that of a translator under ISO 17100: a degree in translation or linguistics, or documented professional experience. The difference lies not in the level of rigour, but in the source material.
An important point for those who follow the sector closely: ISO 18587 is currently under review. The new version, which aligns this standard more closely with ISO 17100 and broadens the scope of hybrid workflows between human translation and AI, is expected to be published by the end of 2026. At Overseas, we currently manage our post-editing (MTPE) services in accordance with ISO 17100 controls, and specific certification to ISO 18587 forms part of our roadmap for our next recertification.
How they are similar (which is in almost everything)
The most frequently asked question when comparing these two standards is: what is the real difference? The short answer is that the input changes, but the quality process does not.
| ISO 17100 | ISO 18587 | |
|---|---|---|
| Starting point | Client’s original text | Machine translation output |
| Required profile | Qualified or experienced translator | Post-editor with equivalent training |
| Revision process | Revision by a second linguist | Revision and validation by the post-editor |
| Quality control | Documented and auditable | Documented and auditable |
| Responsibility | Of the certified provider | Of the certified provider |
| Expected result | Professional-quality translation | Quality equivalent to human translation |
The two standards cover different services. When you commission the translation of a technical contract that leaves no room for ambiguity, ISO 17100 applies. When you commission the revision of a large volume of repetitive content that has already been processed by an AI engine, ISO 18587 applies. In both cases, the chain of responsibility and the requirements for those carrying out the work are comparable.
Why you should insist on ISO certification from your translator
Here is the argument most often omitted from articles on ISO translation standards.
If you have ISO 9001 — the most widely adopted quality management standard — it is because someone decided that internal processes need to be auditable, documented and reproducible. That logic doesn’t disappear when you outsource translation.
When you contract with an uncertified agency, or when you let AI do the translating directly, you have no guarantee that the result follows a rigorous process. The text may sound fine, but there is no audit to verify it, no professional to sign off on it, and no one to take responsibility if something goes wrong. With an agency certified to ISO 17100 or ISO 18587, the standard guarantees that:
- Translators or post-editors meet verifiable competence requirements.
- The process has defined, documented and regularly reviewed steps.
- There is a quality control mechanism in place prior to delivery.
- There is traceability of who did what on each project.
This is no minor detail if you are an industrial company publishing technical manuals in several languages, or if you are submitting documentation for international tenders where a terminological error could lead to exclusion from the process. Nor is it a minor detail if your brand needs to sound just as good in English, French and German as it does in Spanish.
The difference between a tool and a professional
This is where AI comes in, and it is worth being clear.
A machine translation engine is a tool. Very useful, increasingly accurate, and perfectly valid as a starting point in certain workflows. But a tool has no qualifications, has not read the standards of the sector to which your document belongs, and cannot take responsibility when something goes wrong.
Think of it this way: when you take your car to the garage, the mechanic uses computerised diagnostic software. It tells them where the fault might be. But the person who interprets that diagnosis, decides what needs repairing and signs the warranty for the work is the mechanic, with their training and their name on the invoice. Nobody issues the warranty in the name of the diagnostic programme.
Something similar happens with translation. AI gives you a draft. A certified post-editor reads that draft with the expertise of someone who knows the sector, picks up on the nuances the engine can’t detect — the double meaning of a technical term, the client’s style conventions, the right tone for the target market — and delivers something you can publish or present without risk.
You can also look at it from a medical perspective: the radiologist has access to AI systems that detect anomalies in an X-ray. These systems are a real help. But the diagnosis, the clinical decision and the responsibility lie with the doctor. Nobody signs the report on behalf of the algorithm.
The difference is not that AI is bad. It is that professional responsibility cannot be outsourced to an algorithm. A company that commissions translation directly from ChatGPT or DeepL without human review is taking on that responsibility itself — and usually without the knowledge or tools to manage it. If you’d like to explore this further, here we explain when not to use AI for translation.
How we work at Overseas Translations
At Overseas, we offer two distinct services depending on the type of project and the client’s needs.
Professional human translation, covered by our ISO 17100:2015 certification since 2017. The process involves translation by a specialist native speaker of the target language and proofreading by a second linguist. This is the ideal service for contracts, technical documentation, legal texts and marketing materials where terminological accuracy and tone leave no room for error.
Post-editing (MTPE), where we start with the output from DeepL — or the best engine available depending on the text and language pair — using our CAT tool and a human post-editor who reviews, corrects and validates the result. This is the ideal service for large volumes of content with repetitive language, internal documentation, knowledge base updates or platforms with structured text. We apply the quality controls of ISO 17100 whilst preparing for specific certification to ISO 18587 for our upcoming recertification.
What both services have in common is that there is a qualified person behind them who takes responsibility for the final output. That is something no AI subscription can provide.
If you’re unsure which service best suits your project, let us know. We’ll clarify it for you during the call.
Frequently asked questions
What is the difference between ISO 17100 and ISO 18587 in practice?
The difference lies in the starting point of the process, not in the level of rigour. In ISO 17100, the translator works directly on the client’s original text. In ISO 18587, the post-editor works on the output of a machine translation engine and brings it up to the quality standard of a human translation. The competence requirements for the person carrying out the work are comparable in both standards.
Can I use ChatGPT or DeepL directly for my corporate translations?
It depends on the type of document and the level of risk you are willing to accept. For internal content or low-impact texts, it may be sufficient. For technical documentation, contracts, tenders, marketing materials for international markets, or any text where an error could have commercial or legal consequences, you need the involvement of a professional who takes responsibility for the result.
What does an ISO translation certification actually guarantee?
That the agency follows processes audited by an independent body, that the translators or post-editors meet verifiable competence requirements, and that there is traceability for every project. An external audit — in our case, Bureau Veritas — periodically checks that all these requirements are met. It’s not just a piece of paper on the wall: there is a renewal process involving a proper inspection.
Is ISO 18587 suitable for any type of content?
Post-editing works well for content with repetitive language, large volumes and the availability of translation memories or existing terminology glossaries. For creative content, legal texts requiring a high degree of interpretation, or communication where tone is particularly sensitive, direct human translation is the most appropriate option.
Is Overseas Translations ISO 18587 certified?
We currently hold ISO 9001:2015 and ISO 17100:2015 certification, both since 2017 and audited by Bureau Veritas. Specific certification to ISO 18587 is planned for our next recertification. In the meantime, post-editing services are managed in accordance with the controls set out in ISO 17100.
