A client sends an RFP. One line in the requirements section reads: “Machine translation post-editing must comply with ISO 18587.” You’ve been offering MTPE for two years, your editors are good, and clients are generally happy with the output. But do you actually comply with that standard? Would you pass an audit?
If you’re not sure, you’re not alone. ISO 18587 is one of the least-understood standards in the language industry - partly because MTPE itself is newer, and partly because the gap between “we do MT + human editing” and “we comply with ISO 18587” is wider than most people expect.
This article breaks down what the standard actually requires, what post-editor qualifications look like, how certification works and what it costs, and how ISO 18587 sits alongside ISO 17100 in your quality framework.
What Is ISO 18587 and Why It Exists¶
ISO 18587:2017 is the international standard for “translation services - post-editing of machine translation output.” It was published by the International Organization for Standardization in 2017 to fill an obvious gap: as MT adoption accelerated, there was no agreed-upon framework for what “good” post-editing actually looked like.
Before ISO 18587, every agency defined MTPE quality differently. One shop might do a quick skim for obvious errors. Another would do line-by-line editing to publication standard. Both called it “post-editing.” Clients had no way to compare.
The standard establishes two things that matter most: what the process should look like, and what qualifications a post-editor needs to have. It doesn’t say which MT engine to use, or that MT is better or worse than human translation. It just defines the floor for quality when you’re using MT as part of your workflow.
The MTPE services market was valued at $1.59 billion in 2025 and is projected to reach $5 billion by 2035, growing at 12.1% annually. The standard exists because a market that size needs an agreed definition of quality - and ISO 18587 is it.
Full Post-Editing vs Light Post-Editing: Not the Same Thing¶
This is where most people get confused - and where the standard draws its most important line.
ISO 18587 defines two distinct levels of post-editing, and they have completely different quality targets.
Full post-editing aims for output that is comparable in quality to a human translation. The post-editor goes through every sentence and corrects everything: mistranslations, awkward phrasing, terminology errors, style issues, cultural misfires, anything that would make the text read as machine-generated. The end product should be indistinguishable from a professionally translated text.
Light post-editing (also called “rapid post-editing”) targets a lower bar: the text should be correct enough to be understood. Fluency doesn’t matter. Style doesn’t matter. The goal is to make the MT output comprehensible without polishing it.
ISO 18587 primarily covers full post-editing. Light post-editing is mentioned but falls outside the standard’s main scope for quality assurance purposes. If a client asks for “ISO 18587-compliant MTPE,” they’re asking for full post-editing to human-quality standards - not a quick skim.
This distinction matters enormously for pricing. Full post-editing runs $0.08-0.15/word - roughly 50-75% of pure human translation rates. Light post-editing is $0.02-0.06/word. Quoting one when the client needs the other creates problems at delivery.
The Six Post-Editor Competences¶
One of the most specific - and most demanding - parts of ISO 18587 is its competence framework. A qualified post-editor isn’t just someone who speaks both languages and can spot an error. The standard requires documented competence across six areas.
According to intertranslations.co.uk, the six required competences are:
1. Translation competence - the ability to produce a translation that meets quality standards for the intended purpose. This includes understanding of source text, accurate rendering of meaning, and appropriate register.
2. Linguistic and textual competence - proficiency in both the source and target languages at a professional level. Not just fluency - the kind of command over register, idiom, and style that a native-speaker professional writer would have.
3. Research, information acquisition, and processing competence - the ability to find and evaluate terminology resources, reference materials, and domain-specific sources efficiently. Post-editors can’t stop work every time they hit an unfamiliar term.
4. Cultural and social competence - understanding of the cultural context behind both the source and target texts. MT frequently fails on cultural references, humor, idiomatic expressions, and localized conventions. The post-editor needs to catch these.
5. Technical competence - ability to work with CAT tools, MT system interfaces, translation memories, and terminology databases. Post-editing happens in specific tools, and the post-editor needs to be genuinely proficient with them.
6. Domain competence - specialist knowledge of the subject matter being translated. A post-editor working on pharmaceutical regulatory submissions needs different background knowledge than one working on marketing copy.
All six competences must be present. Missing even one - say, weak domain knowledge on a technical project - means the post-editor doesn’t meet the standard’s qualifications for that work.
Qualification Requirements: Who Can Post-Edit Under ISO 18587¶
The competences describe what a post-editor needs to know. The qualification requirements describe the credentials that serve as evidence of those competences.
ISO 18587 accepts three paths to qualification, mirroring the structure in ISO 17100 for translators:
| Path | Requirements |
|---|---|
| Translation degree | Higher education degree in translation, linguistics, or language studies with substantial translation training |
| Any degree + experience | Any higher education degree + equivalent of 2 years full-time professional translation or post-editing experience |
| Experience only | Equivalent of 5 years full-time professional translation or post-editing experience, no degree required |
The key word in all three paths is “professional.” Casual bilingualism or informal translation work doesn’t count. The standard is looking for post-editors who can demonstrate they’ve been doing this work at a professional level.
Agencies that use freelance post-editors need to collect documentary proof for each person: degree certificates, CVs, portfolios, client references. “They do good work, I’ve checked” is not sufficient under the standard. If an auditor asks to see your post-editor qualification records and you can’t produce them, that’s a non-conformity.
ISO 18587 vs ISO 17100: Understanding the Difference¶
These two standards are complementary, not competing. They cover different workflows - but agencies doing both types of work need to understand where each applies.
As certly.me explains, the core difference comes down to what initiates the translation:
| Criterion | ISO 17100 | ISO 18587 |
|---|---|---|
| Primary workflow | Human translation from source | Machine translation + human post-editing |
| Starting point | Translator works from the source text | Post-editor works from MT output |
| Raw MT output | Explicitly excluded from scope | Core input of the process |
| Translator/post-editor qualifications | Detailed requirements | Six competences + three qualification paths |
| Mandatory second review | Required (revision by different person) | Required for full post-editing |
| Target quality | Publication-ready human translation | Publication-ready (full PE) or comprehensible (light PE) |
| MT engines/tools | Not applicable | Covered in process requirements |
| Current status | ISO 17100:2015, revision expected ~2029 | ISO 18587:2017, revision expected end 2026/early 2027 |
One important point: you can hold both certifications simultaneously. For agencies offering both pure human translation and MTPE, running a combined audit saves money - certification bodies can cover both standards in a single visit.
According to transpose.ch, agencies certified to both standards send a clear market signal: “we have documented, audited quality processes for every type of translation workflow we offer.” That’s increasingly what enterprise procurement departments want to see.
Process Requirements: What ISO 18587 Actually Specifies¶
Beyond post-editor qualifications, the standard defines what the MTPE process should look like from start to finish. CertBetter’s guide and exact-gmbh.com both break this down into three phases:
Pre-production¶
Before post-editing starts, the agency must:
- Assess suitability of the source content for MT (not everything is appropriate - legal or heavily idiomatic texts may produce MT output too poor to post-edit efficiently)
- Select an MT engine appropriate for the content type and language pair
- Define whether full or light post-editing is required - and document that decision
- Assign post-editors with the right competences for the specific domain
- Brief the post-editor on client-specific style guides, terminology preferences, and target audience
This pre-production assessment is often the step agencies skip. Running content through MT and handing it to an editor without any assessment is fast, but it’s not ISO 18587 compliant.
Production¶
The core editing phase has specific requirements:
- Post-editing follows documented guidelines (not the post-editor’s personal approach)
- All MT errors are identified and corrected: accuracy errors, fluency issues, terminology mismatches, cultural problems
- Changes are tracked in a way that allows audit and review
- For full post-editing, a second review is performed by a different qualified post-editor or translator
That last point is worth emphasizing. Full post-editing under ISO 18587 requires the same four-eye principle as ISO 17100 translation: the same person who did the initial post-edit cannot be the only reviewer. A second qualified person reviews the output.
Post-production¶
After editing is complete:
- Delivery of post-edited content in the agreed format
- Documentation of the project: which MT engine was used, post-editor assignments, review records
- Feedback mechanism so clients can flag issues after delivery
- File storage and confidentiality procedures
The documentation requirements are more extensive than most agencies expect. Every project needs a paper trail that would allow an auditor to trace who did what, when, and in what tool.
Certification: How to Get It, Who Certifies, What It Costs¶
Getting certified to ISO 18587 follows the same two-stage audit process as other ISO management system standards.
Stage 1 (documentation audit): The auditor reviews your written procedures, policies, and records. Does your documentation describe processes that would comply with the standard? Do your post-editor qualification records look complete? Are there gaps or non-conformities? If issues are found, you get a corrective action period before Stage 2.
Stage 2 (implementation audit): The auditor checks whether you actually follow the processes described in your documentation. This includes interviewing post-editors, reviewing actual project records, checking that MT suitability assessments happened, confirming that second reviews are being done. Stage 2 is where “certified for show” agencies get caught.
After certification, annual surveillance audits check that you’re maintaining the standard. Full re-certification every 3 years.
Who Certifies¶
Major certification bodies for ISO 18587 include:
- TÜV SÜD - one of the most recognized international certification bodies, often certifies ISO 17100 and ISO 18587 together
- Linquacert - specialist language industry certification body
- USQC - US Quality Certification, North American focus
- Orion Assessment Services - significant presence in the translation industry, 300+ language company clients
One of the earliest agencies to get ISO 18587 certified was oneword GmbH, who achieved certification in 2019. They hold both ISO 17100 and ISO 18587, which is becoming the expected combination for agencies offering both workflow types.
What It Costs¶
For a small agency (2-5 people), expect:
| Cost Item | Estimate |
|---|---|
| Certification audit (Stage 1 + Stage 2) | €3,000-€5,000 |
| Preparation consultant (optional) | €2,000-€5,000 |
| Internal time for documentation preparation | 40-80 hours |
| Annual surveillance audit | €1,500-€2,500 |
For a larger LSP (20+ people, complex workflows), total first-year cost including certification, consultant, and internal time can exceed €10,000.
If you’re combining ISO 18587 with ISO 17100 in a joint audit, the total cost is lower than two separate audits. Most certification bodies can cover both standards in the same visit, which typically saves 20-30% compared to separate certifications.
The certificate is valid for 3 years. After that, full re-certification.
Who Needs ISO 18587¶
Agencies that should get certified¶
LSPs with significant MTPE volume going to enterprise clients. If corporate clients, pharmaceutical companies, law firms, or government agencies are asking for ISO 18587 in their RFPs, that’s a direct business requirement. Not having the certificate means not being in the running.
“The adoption of MTPE has jumped from 26% in 2022 to 46% in 2024, per Nimdzi’s industry surveys. As MTPE becomes mainstream, the certification that governs it becomes a mainstream requirement.”
Agencies building MTPE as a primary offering. If you’re positioning yourself as an MTPE specialist - not just “we sometimes use MT to speed things up” but a deliberate workflow - ISO 18587 is the credibility signal that separates you from agencies that just use DeepL and call it MTPE.
Agencies already certified to ISO 17100 that have added MT workflows. If you’re ISO 17100 certified but now doing significant MTPE volume, you’re operating outside your certified scope for that work. Adding ISO 18587 closes that gap cleanly.
Who doesn’t need it (yet)¶
Agencies using MT only for internal reference. If post-editors glance at MT output as one reference among several but always translate from scratch, that’s ISO 17100 territory, not 18587.
Small freelance operations. Certification overhead - the documentation, the audits, the maintenance - is hard to justify when you’re one person. The more useful move for freelancers is demonstrating the six competences to clients informally: your credentials, your domain knowledge, your tool proficiency.
Agencies with no corporate clients requiring it. If your client base is SMBs and individuals who’ve never heard of ISO 18587, the ROI calculation gets very thin. The market signal only works if the buyers you’re trying to reach know what it means.
What’s Changing: The 2026 Revision¶
ISO 18587:2017 is currently being revised. The new version is expected at the end of 2026 or early 2027, according to ATC Certification’s analysis.
The revision is driven by how dramatically MT technology has changed since 2017. When the current standard was written, neural MT was new. Large language models didn’t exist in their current form. Adaptive MT, real-time MT, AI-assisted translation - these were not part of the landscape the standard was designed for.
What’s expected to change, based on the EUATC April 2026 webinar on ISO 17100 and 18587:
Convergence with ISO 17100. The two standards are expected to move toward a unified framework, with shared requirements for competences and process management. Agencies holding both will need less duplication in their documentation.
Risk-based approach. Instead of prescribing specific process steps, the new version is expected to take a more risk-based stance: define the quality outcomes required, let agencies determine the specific process steps that achieve those outcomes. This is a significant philosophical shift.
AI workflow coverage. The revision will address workflows that go beyond traditional MT + post-editing: adaptive MT systems that learn from post-editor corrections, AI tools that assist rather than replace, hybrid pipelines where the boundaries between translation and post-editing blur.
Technology neutrality. The current standard is somewhat tied to the MT technology paradigm of 2017. The new version is expected to be written in a way that doesn’t become obsolete as MT technology continues to evolve.
As EUATC noted:
The revision reflects the industry’s shift toward AI-assisted workflows and aims to create a framework that remains relevant as technology continues to evolve. The convergence between ISO 17100 and ISO 18587 acknowledges that the boundary between human translation and MTPE is increasingly fluid.
If you’re planning to get certified, it’s worth being aware that the standard you certify to in 2026 will be replaced within a year or two. That doesn’t mean you shouldn’t certify now - the current standard is still the basis for client requirements and tenders - but build your processes with the upcoming changes in mind.
Common Implementation Mistakes¶
Most agencies that attempt ISO 18587 compliance without external guidance hit the same set of issues.
Using MT without suitability assessment. Throwing every project through the same MT engine regardless of content type, language pair, or intended use is not ISO 18587 compliant. The standard requires that you assess whether MT is appropriate before you use it. Some content types consistently produce poor MT output - legal documents with complex jurisdiction-specific language, highly idiomatic marketing copy, texts with unusual formatting. Using MT on these without evaluation and then post-editing the mess costs more time than translating from scratch.
No documented post-editing guidelines. The standard requires that post-editors follow documented guidelines, not their personal judgment. If your agency has no written guidelines for what constitutes a complete post-edit, what level of editing is expected, and how MT errors should be handled, that’s a gap. Post-editing guidelines don’t need to be long - a clear 2-page document covering the expected editing scope, tool requirements, and quality criteria is usually enough.
Skipping the second review. For full post-editing, ISO 18587 requires a second qualified person reviews the output. Many agencies skip this - it takes time, it costs money, and when the MT output is good and the post-editor is experienced, it can feel unnecessary. But “feels unnecessary” is not the standard. If you’re claiming ISO 18587 compliance for full post-editing, every deliverable needs that second review.
Inadequate post-editor qualification records. As with ISO 17100 for translators, the standard requires documented evidence of post-editor qualifications. Degrees, CVs, portfolios, proof of domain expertise. “They’ve been doing this for years” is not a record. Collecting and maintaining these records is operational overhead that agencies consistently underestimate.
Conflating light and full post-editing in client agreements. Agreeing to “ISO 18587-compliant MTPE” without specifying full vs. light post-editing creates scope ambiguity. The client may assume they’re getting full post-editing to human quality; you may be pricing and resourcing for light post-editing. Clarify this in writing before every project.
MTPE Pricing Under ISO 18587¶
Running a genuinely ISO 18587-compliant MTPE workflow costs more than most agencies initially budget for. Understanding why matters for pricing your services correctly.
The cost drivers in a compliant full post-editing workflow:
- Post-editor time: Full post-editing of good MT output runs 300-500 words/hour. Poor MT output, or complex specialized content, can drop to 150-200 words/hour. Budget based on your actual MT quality, not theoretical productivity.
- Second review: A second qualified reviewer adds 10-20% to the time cost. Many agencies absorb this by having the PM do a lighter check, but a genuine second review by a qualified post-editor is more expensive.
- Pre-production assessment: MT suitability evaluation, briefing the post-editor, setting up terminology resources - this non-billable time needs to be factored in.
- Documentation: Maintaining project records, qualification records, and audit trails is ongoing administrative work.
What does this translate to in real rates? According to Nimdzi’s MTPE pricing research, full post-editing runs $0.08-0.15/word. Light post-editing is $0.02-0.06/word.
For context, pure human translation for general content typically runs $0.10-0.20/word. That puts compliant full post-editing at 50-75% of human translation rates - a meaningful discount, but nowhere near the 80-90% discounts some clients expect when they hear “machine translation.”
On the translator side, pricing MTPE work is not straightforward. According to GTS Translation’s 2025 survey of translators, 50% of translators don’t offer MTPE discounts at all - arguing that good post-editing requires as much skill and effort as translation and shouldn’t be priced lower. Those who do discount typically apply a 10-30% reduction.
As Seatongue’s analysis of post-editing pricing points out:
The “post-editing trap” is accepting lower rates on the assumption that MT does most of the work. In practice, poor MT output can take longer to fix than translating from scratch. Pricing should reflect actual time, not the theoretical productivity gains that MT vendors advertise.
For agencies building ISO 18587-compliant workflows, the bottom line is: price based on what the workflow actually costs, not on the discount clients assume they deserve because MT is involved. If your full post-editing workflow costs 70% of human translation to deliver, price it at 70% - not 40%.
FAQ¶
What is the difference between ISO 18587 and ISO 17100?¶
ISO 17100 covers pure human translation and explicitly excludes MT post-editing from its scope. ISO 18587 covers machine translation post-editing specifically - when an MT engine produces the initial output and a human post-editor refines it. If you offer both workflows, you need both standards. They’re designed to be complementary and can be audited together in a single certification visit.
Is ISO 18587 certification required by law?¶
No. ISO 18587 is a voluntary standard, not a legal requirement. However, it’s increasingly written into enterprise procurement requirements and tender specifications. “Required by law” and “required to win the contract” are different - but the practical effect is similar.
Can a freelancer comply with ISO 18587 without getting certified?¶
A freelancer can comply with the standard’s requirements - the right qualifications, documented processes, consistent quality - without going through formal certification. Certification is an independent audit that verifies compliance; compliance itself doesn’t require certification. Many freelancers implement ISO 18587-aligned workflows and communicate that in proposals without holding a formal certificate.
How long does ISO 18587 certification take?¶
For a small agency with organized processes, plan for 3-4 months from starting preparation to receiving the certificate. If you’re starting from scratch on documentation and processes, allow 5-6 months. The actual audit (Stage 1 + Stage 2) takes a few days; the preparation before it is where the time goes.
Does ISO 18587 apply to AI translation tools beyond traditional MT?¶
The current 2017 version was written for traditional MT systems. It’s being interpreted broadly to cover neural MT and modern AI translation tools, but the upcoming 2026/2027 revision will explicitly address contemporary AI workflows. If you’re using large language models, adaptive MT, or AI-assisted translation tools, the spirit of the standard applies even if the letter is ambiguous. The revision will resolve that ambiguity.
What happens if I use MT without telling the client?¶
This is a separate issue from ISO 18587 certification - it’s an ethical and sometimes legal one. Several jurisdictions and professional bodies require disclosure when MT is used. ISO 18587 compliance doesn’t require client disclosure per se, but the standard’s process requirements (including MT suitability assessment and documented workflows) create an implicit expectation of transparency. If a client later discovers undisclosed MT use, the certification doesn’t protect you from the reputational or legal consequences.
What’s a realistic MTPE productivity rate for budgeting?¶
For good-quality neural MT output in common language pairs (EN-DE, EN-FR, EN-ES): 400-600 words/hour for full post-editing. For specialized or technical content with more MT errors: 200-350 words/hour. For light post-editing of reasonably clean MT: 800-1,200 words/hour. These are industry ranges - your actual rates will vary by language pair, MT engine quality, and content type. Track your real productivity data; don’t use vendor-quoted figures.