I Built 6 Free SEO Tools in One Day — Here's What I Learned
Published: (April 5, 2026 at 09:38 PM EDT)
3 min read
Source: Dev.to
Source: Dev.to
Introduction
SEO tools are everywhere, but most are locked behind sign‑ups, API limits, or subscription walls. I wanted something I could actually use without friction, so I built six tools over a weekend and open‑sourced the approach. All run in‑browser (four client‑side) or via lightweight server fetch (two API routes), with zero external API costs.
What the tools do
| Tool | How it works | Key benefits |
|---|---|---|
| Schema Generator | Visual form → valid JSON‑LD for FAQPage, Article, HowTo, Product, Organization, BreadcrumbList. Click “Copy HTML” and paste into your “. One‑click link to Google Rich Results Test. | Generates structured data in seconds instead of manually typing it. |
| LLMs.txt Generator | Input any URL, fetch its sitemap, extract titles/descriptions, format everything into llms.txt + llms-full.txt following the llmstxt.org standard. | Provides the file AI assistants (ChatGPT, Claude, etc.) use for citations; missing llms.txt means missed citations. |
| Hreflang Builder | Add language/URL pairs, get self‑referential hreflang HTML with x-default. Validates duplicate and missing tags. | Saves ~10 minutes each time a new language is added to a site. |
| Meta Analyzer | Pixel‑accurate truncation check (Google measures in pixels, not characters). Live SERP preview, keyword‑density analysis, power‑word detection. Flags “Best”/“Top” in titles per Google’s Feb 2026 Core Update rules. | Ensures titles and meta descriptions are optimised for Google’s display limits. |
| Robots.txt Tester | Paste your robots.txt, test any URL path against 15+ user agents (including GPTBot, ClaudeBot, PerplexityBot, Google‑Extended). Shows which rule matched and whether it’s Allow or Disallow. | Verifies that AI crawlers are correctly blocked or allowed. |
| OG Preview | Fetch any URL and see how it renders on Twitter, LinkedIn, Slack, and Discord. Each platform crops differently; the tool shows all four previews and detects missing or broken tags. | Guarantees consistent social sharing previews across major platforms. |
Why I built them
- I was manually typing JSON‑LD for every blog post. The Schema Generator reduces that to ~30 seconds.
- AI assistants rely on
llms.txtfor site citations; without it, you lose visibility in AI‑generated answers. - Managing multilingual hreflang tags is error‑prone; the Hreflang Builder automates validation.
- Title and meta‑description truncation is measured in pixels, not characters; the Meta Analyzer gives a realistic preview.
- Blocking AI crawlers is becoming the default, yet many sites don’t know if their
robots.txtrules actually work. - Social preview inconsistencies cause missed click‑throughs; the OG Preview consolidates platform‑specific crops.
Architecture
- Client‑side first – Four of the six tools run entirely in the browser. No server, no API, no data retention.
- Server fetch only when needed – The LLMs.txt Generator and OG Preview need to fetch external URLs (CORS), so they use Next.js API routes.
- Zero API cost – No OpenAI or paid APIs; the tools rely on
fetch()and regular‑expression parsing. - Dynamic routing – A single
[tool]/page.tsxhandles stubs for unreleased tools; specific routes override when ready.
Known limitations & future work
- Schema Generator – Currently only generates JSON‑LD; client‑side validation against the Schema.org spec could be added.
- Meta Analyzer – Pixel‑width estimation is approximate; a Canvas‑based measurement would improve accuracy.
Availability
All six tools are live at . No sign‑up, no API key required. Feedback is welcome.
Call to action
What free SEO tools do you actually use daily? Let me know what’s missing from the landscape.