The Market Has Gotten Crowded — Here's How to Evaluate It
A few years ago, DET prep meant a PDF guide and maybe a tutor. Now there's a genuine market of platforms offering mock tests, AI-scored writing and speaking feedback, and personalized study plans — Arno, DET Practice, DET Ready, and others, alongside Prepingo. Most of them advertise similar-sounding features, which makes the marketing hard to tell apart even though the platforms themselves aren't identical.
Rather than rank platforms against each other on claims that are hard to verify from the outside, it's more useful to know what actually separates a good DET prep tool from a mediocre one. Here's what to check before you commit to (or pay for) any platform.
1. Does the Mock Test Match the Real Test's Length and Format?
Duolingo's own free practice test is shorter than the real exam and gives a broad estimated range rather than a precise score. That's fine as a first look at the interface, but it's not a substitute for a full-length mock. A prep platform's mock test is worth more if it:
- Runs close to the real exam's roughly 60-minute length
- Includes every question type you'll actually see — Write/Speak About the Photo, the Writing and Speaking Samples, Interactive Reading/Listening, not just multiple choice
- Gives you subscores, not just one overall number
A short, fixed-length quiz that skips the Speaking and Writing Samples will feel easier than the real test and won't tell you much about your actual score.
2. How Is Your Writing and Speaking Actually Graded?
This is the part that varies most between platforms, and it's worth checking directly rather than taking marketing copy at face value. Ask, or test for yourself:
- Does the feedback go beyond spelling and grammar? The real DET rubric also scores content relevance, how logically your ideas connect, and vocabulary range — not just whether your sentences are grammatically correct.
- Do you get a score, or just a correction? A platform that rewrites your answer for you is useful for seeing a model response, but it doesn't tell you where your own response would have landed.
- Is the feedback specific? "Good job, try using more varied vocabulary" is vague. Feedback that points to particular sentences and explains what's holding the score back is more useful.
Several platforms, including Prepingo, market AI grading aligned with the official rubric categories. Where you can, test this with a free sample before paying — submit the same response on more than one platform and compare how specific and consistent the feedback is.
3. Does It Prepare You for the Proctoring Experience?
A meaningful number of test-takers who get asked to retake the DET aren't flagged for cheating — they're flagged for things like looking away from the screen too often, having other people visible in the room, or unstable lighting that makes it hard to confirm who's on camera. Some prep platforms now include practice modes that use your webcam to flag this kind of behavior during mock sessions, which is genuinely useful preparation if you've never taken a heavily proctored exam before. If a platform offers this, it's worth using a few times before your real test, even briefly.
4. Free Tier vs. Paid Tier: What's Actually Worth Paying For
Most platforms, Arno included, offer a meaningful amount for free — large practice question banks, limited AI feedback samples, or one free mock test. The paid tiers generally unlock unlimited AI feedback, full mock test access, and personalized study plans. Before subscribing anywhere:
- Use the free tier first and see if the feedback style actually helps you improve, not just whether it sounds sophisticated.
- Check whether pricing is a flat subscription or a credit system — credit systems can get expensive quickly if you want detailed feedback on every practice response.
- Confirm the platform is still being updated for the current test format. The DET, like other major English tests, has had format changes in recent cycles, and prep content that hasn't kept up will teach you the wrong question types.
Where Prepingo Fits
Prepingo offers full-length mock exams built around the real test's timing and question mix, AI-scored writing and speaking feedback mapped to the official rubric categories, and a webcam practice mode aimed at the proctoring habits described above. If you're comparing platforms, the most useful thing you can do is try the free tools on a couple of them with the same practice response and see which feedback actually helps you fix something specific — that tells you more than any feature list, including this one.
FAQ
Is a free mock test enough to prepare?
It's a reasonable starting point to learn the interface and question types, but free official practice tests are shorter than the real exam and give a score range rather than a precise number. A full-length, subscore-reporting mock test gets you closer to a reliable estimate.
What should I look for in AI writing feedback?
Specificity. Feedback that names which sentences are weak and why is more useful than a general score or an automatically rewritten "better" version of your answer, since you need to understand what to fix yourself.
Do I need a paid platform to reach a high score?
Not necessarily. Many platforms offer substantial free practice. Paid tiers are most worth it if you specifically need detailed, repeated AI feedback on writing and speaking, since that's harder to get for free elsewhere.