Dev.to
7/28/2026
The original headline is "10 lessons from building 120+ free online tools as a solo developer"
Original: I Built 120+ Free Online Tools. Here Are 10 Mistakes I'd Never Make Again.
Short summary
A solo developer shares 10 hard-learned lessons from building 120+ free online tools (DukoTools). Key takeaways: launch early with 10-20 tools, boring tools (PDF merger, image compressor) get more traffic than clever AI ones, niche tools win SEO with near-zero competition, and browser APIs eliminate backend costs. Marketing must happen alongside building, not after.
- •Launch early with 10-20 tools, let users guide what to build next
- •Boring utility tools outperform clever AI tools in actual usage
- •Niche tools (e.g. regional calculators) are an SEO superpower with minimal competition
- •Browser APIs reduce hosting costs and improve privacy; Docker can prevent cold-start issues
Generated with AI, which can make mistakes.
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