Prompt-Engineering Practical Guide for Localization Teams
A prompt is simply a set of written instructions you give to an AI model so it knows how to translate, rewrite, or post-edit your content.
For localization professionals, a prompt is the AI equivalent of a style guide + brief + termbase instruction, packed into one task description.
The effect of poorly specified constraints in translation prompts
Prompt engineering is the skill of writing clear instructions for an AI model.
You don’t need a computer science degree.
You don’t even need to be a “prompt guru.”
If you can:
…then you already understand the core of prompt engineering.
Before going deeper, let’s see what makes up a strong prompt and the key terminology behind it.
Prompts start by defining the translator’s role, for instance, a specialist in finance, law, or UI design. This frames tone, terminology, and context.
Role: You are a professional translator specializing in [FIELD]. Translate and post-edit UI text (buttons, menus, notifications, tooltips, system messages) into French (France). Ensure translations are clear, concise, and user-friendly.
Instructions are the backbone of any prompt—clear, specific directions that tell the model exactly what you want, in the format you expect, with explicit rules like “Do not add, omit, or invent details” to prevent hallucinations and keep outputs reliable.
Follow all guidelines strictly. Do not skip or ignore any rules. The instructions are grouped into chapters:
Preserve all original formatting, including HTML, Markdown, placeholder variables, line breaks, and whitespace.
Interpret backslash-n as a line break.
Retain all tags and syntax without modification.
Maintain non-breaking spaces as they appear in the source text.
Use an informal tone with “tu” throughout.
Prefer active voice over passive constructions.
Translate English “-ing” forms as infinitives or nouns, avoiding gerunds.
Ensure consistent tense usage, using imperative for lists where applicable.
Follow French capitalization rules: capitalize only the first word in titles/headers, proper names, and the first word after a period.
Use commas for decimals (e.g., 1,25).
Write four-digit numbers without separators (e.g., 1500).
Use non-breaking spaces for five-digit or larger numbers (e.g., 10 000).
Place currency symbols/codes or percent signs after the number with a non-breaking space (e.g., 25,50 €, 15 %).
Add a non-breaking space between numbers and units.
Use dd/mm/yyyy format (e.g., 25/06/2025).
Use 24-hour clock format with “h” and colons (e.g., 8h30, 14h45).
Do not translate product/feature names or brand names (e.g., [PRODUCT_NAME], [BRAND_NAME]); keep them in English.
Ensure terminology is professional, consistent, and suitable for UI contexts.
Post-editing rules define how you want the model’s output refined—what to fix, what to avoid, and what quality standards the final text must meet.
Replace guillemets (« ») with quotation marks (” “).
Remove spaces between numbers and the percent sign (e.g., 15% instead of 15 %).
Ensure commas are used for thousands and periods for decimals in English text; rewrite if incorrect (e.g., 1,000.25 → 1.000,25 for French).
For non-French text, ensure grammatical correctness and clarity without translating brand names.
Use em dashes (—) where appropriate in non-French text.
Simplify technical English when applicable, ensuring clarity and conciseness.
Preserve symbols, dots, or delimiters as they appear.
Concrete examples are one of the most powerful parts of a prompt. For instance:
SOURCE:
“Welcome, <username>!\nJoin our <product_name> community today. Get 15 % off on 25/06/2025 at 14:45 PM.”
OUTPUT:
“Bienvenue, <username> !\nRejoins notre communauté <product_name> aujourd’hui. Obtiens 15% de réduction le 25/06/2025 à 14h45.”
Variables let you insert dynamic inputs—such as product names, languages, or style choices—so the same prompt can be reused flexibly without rewriting it each time.
The output format defines how you want the model’s response to be structured—such as bullets, tables, JSON, or full paragraphs—so you consistently receive results in the exact shape you need.
In localization prompts, the input text—the content you want translated or adapted—should be placed at the end of the prompt.
This is the section where the actual source text is placed for translation. It comes after all instructions, variables, and examples so the translator or model has full context before starting the task.
Prevent with explicit rules: “Do not add, omit, or invent details.”
Use glossaries or ask AI to flag unclear terms.
Instruct AI to neutralize offensive language and flag content for review.
Remind AI to adapt idioms and references.
Keep prompts concise for high-volume or API workflows.
Use glossaries or ask AI to flag unclear terms
Get started right now. Download our Professional Prompt Template and start refining your translations in less than two minutes.
Now that you understand how professional prompting works, the next step is to put it into practice.
For deeper learning, browse our articles on prompt engineering, watch recordings from GenAI conferences and workshops.
If your team needs hands-on training, you can book a Custom.MT workshop to learn how to manage prompts across all your projects.
Request a workshop on prompt engineering in localization
A localization prompt is a structured instruction for AI or MT to produce accurate, consistent translations with the right tone, terminology, and formatting. Custom.MT’s Prompt Studio lets you create, test, and deploy prompts safely for MT, APE, QE, and GenAI workflows.
Prompts guide AI output, while TMs store previously approved translations. Together, they ensure consistency, speed up translation, and reduce manual post-editing.
Yes. Prompts can be adapted for different languages by updating variables such as source/target languages, tone, and style, saving time across projects
Yes, when you provide glossaries or style rules. Prompts enforce brand terms, domain-specific vocabulary, and formatting automatically.
Yes. Prompts can be adapted for different languages by updating variables such as source/target languages, tone, and style, saving time across projects
Prompts are deployed via Custom.MT integrations or extensions, directly inside your workflow, letting AI-enhanced translation work alongside your CAT tool.
Depending on the model and instructions, prompts can preserve technical elements like HTML, curly brackets, placeholders and tags to minimize manual formatting fixes.
Keep prompts clear, structured, role-specific, and rule-based. Test them in Prompt Studio, use examples, and adjust temperature for the right creativity vs. stability balance.
We offer guides, workshops, video tutorials, and hands-on support to help teams implement prompts safely and effectively in their localization workflows.