VoyaLang VS Diffyn

VoyaLang's answer

VoyaLang is built only for IELTS Writing, so every part of the feedback follows the four official criteria instead of general writing advice.

• Each Task 1 visual type is handled on its own terms: line graphs, bar charts, pie charts, tables, process diagrams, maps, and mixed charts.
• General Training letters are checked by type and register, not treated like essays.
• Scores stay consistent, so the same essay does not get a different band each time it is submitted.
• The rewrite is at the student's own target band, so they can see exactly what that band looks like in their own words.
• Teachers can grade on top of it for free: each essay arrives already scored, and the grade a teacher gives becomes the student's grade.

Diffyn's answer:

Addresses workflow and change management on LLM prompts, provide teams with traceability and visualization of tests across multiple models, provide deeper understading into efficiency of these prompts.

VoyaLang's answer

• It covers the whole exam: IELTS Academic and IELTS General Training, Task 1 and Task 2, including charts, maps, process diagrams, and letters.
• The feedback is something you can act on: a band for each criterion, every correction explained, and your answer rewritten at your target band.
• Scores stay consistent, so progress over weeks of practice means something.
• It is free: a free account grades up to 10 essays, with no card and no paid plan.
• It respects your data: built and hosted in Germany, GDPR-compliant, and you can export or delete everything yourself.

Diffyn's answer:

Diffyn is the platform that specializes on both change management and multi-model analysis.

VoyaLang's answer

• Backend: Python, FastAPI, PostgreSQL
• Frontend: Next.js, React, TypeScript, Tailwind CSS
• AI: large language models
• Infrastructure: Docker, hosted in Germany, with Sentry for error tracking

Diffyn's answer:

React, Next.js, POSTGRESQL

VoyaLang's answer

• IELTS candidates preparing for university admission, work, migration, or professional registration, who need honest feedback on their writing before test day.
• IELTS teachers and tutors who run writing classes and want every essay already scored and corrected before they give the final grade.

Diffyn's answer:

Professionals incorporating LLMs or AI tools in their workflow and wants to keep track of changes and test their prompts.

VoyaLang's answer

I took IELTS myself to study in Germany. I could practise reading and listening on my own and find someone to talk to for speaking, but writing was the one section I could not practise alone, because nobody could mark it. Human marking costs money and takes days, and generic AI tools gave a different score every time.

So I built VoyaLang: IELTS Writing feedback that follows the official criteria, stays consistent, and comes back in under a minute. Today it also includes a free panel for teachers who want the first read done before they grade.

• Maryam Mohebi, founder

Diffyn's answer:

I started working on Diffyn when I notice that prompting has become an essential part of work across many industries. While there are version control platofrms like github, they are not designed for just prompt management are can be overkill such applications, it is also not integrated natively with various LLMs and relevant tools for users to validate ideas and visualise results properly.

VoyaLang's answer

• Individual IELTS test-takers preparing on their own. VoyaLang does not have any company or school customers to name yet.