Introduction 📝:
I'm a software engineer and full-stack AI developer. I usually write about code and frameworks. This time I want to show you a real product I've been building: AnzeigenBoost.
It's a Chrome extension that automates selling on Kleinanzeigen.de - Germany's biggest classifieds site. Millions of people use it every day to buy and sell second-hand stuff.
The problem 😩:
If you sell things online, you know this feeling: you post an ad, it gets some views, then it sinks in the search results. A few days later, nobody sees it anymore. So you repost it. Again and again.
AnzeigenBoost does this for you:
It also uses AI to write better ad titles and descriptions, checks where your ad ranks, and shows you what other sellers are doing.
Why Kleinanzeigen 🇩🇪
Kleinanzeigen is huge in Germany. But the tools for sellers are still pretty basic. Search "Kleinanzeigen automation" and you'll find a handful of small tools, not a real ecosystem. That gap is why I built this.
The stack 🏗️:
- Chrome extension - runs inside your own Kleinanzeigen login. No fake accounts, no bots pretending to be you. It just automates what you'd do by hand.
- NestJS backend - handles credits, scheduling, and talks to the AI provider.
- Stripe - pay-as-you-go credits. No subscription trap. AI - writes optimized titles and descriptions, and helps decide the best time to repost an ad.
Features today 🧰:
- Smart Repost - refreshes your ad with a real change (title, photo order, or price), not a copy-paste repost
- Manual Repost - fixed-interval reposting, for people who want full control instead of AI timing
- AI Optimize - rewrites titles and descriptions to be clearer and more likely to get a click
- Photo Check - flags weak or low-quality photos before you post
- Position Check - shows where your ad actually ranks in search
- Competitor Tracking - see what similar sellers are doing with their listings and pricing
The AI side 🤖:
AI shows up in two places right now:
- Listing optimization - takes your rough title/description and rewrites it to be clearer, more complete, and closer to how a real buyer searches.
- Smart timing - instead of reposting on a fixed schedule, the system predicts a better time to repost, based on real signals, not just "every 24 hours."
I'm also exploring AI for the Competitor Tracking side - summarizing pricing trends automatically instead of just showing raw numbers.
What AI actually costs me 💸
This is the part people don't usually talk about. Every AI Optimize action calls a paid AI API - so it's not free compute, it's a real per-action cost that has to be covered by the credit price.
Getting this balance right is one of the harder parts of pricing the product:
charge too little per AI action and it's a loss on paper the moment someone uses it a lot; charge too much and nobody uses the feature at all.
Right now credits are priced with that cost baked in, but it's something I'm still tuning as real usage data comes in.
Smart Repost, the main feature 🔁:
Instead of just reposting the same ad over and over, AnzeigenBoost changes something real each time - a slightly different title, a reordered photo, a small price change. This matters because Kleinanzeigen only re-ranks an ad in search if it looks like a genuine update, not a copy-paste repost.
How it all fits together 🏗️
Under the hood: the Chrome extension talks to the NestJS backend, which handles billing through Stripe, talks to Kleinanzeigen through your own logged-in session, and calls the AI provider for listing optimization.
Challenges along the way 🧗:
- No official API — everything runs through the same interface a human seller uses
- Repost mechanism — delete+recreate resets view counts and doesn't match Kleinanzeigen's own ranking system. Moving to edit-in-place instead
- Looking human, not automated — too-frequent or unchanged reposts look scripted. Took real iteration to get right
- Pricing AI fairly — every AI call has a real cost that has to be covered by credits
Where things stand today 📊:
- Live on the Chrome Web Store, 4-star rating, real users Credits system just launched Right now I'm improving how reposting works under the hood, so it matches how Kleinanzeigen's own system is designed to work - and keeps your ad's views and saved-by-buyers status instead of resetting them every time
Why I'm writing this 📣:
I'm looking for people who actually sell on Kleinanzeigen to try AnzeigenBoost and tell me what's broken or missing. If that's you, or you're just curious how a small AI-powered tool gets built for a specific market - I'd love to hear from you.
🔗 anzeigenboost.de free to try.
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