Does it preserve the order of words?

Yes. The first occurrence of each word is kept, and the order is preserved.
Is the comparison case-sensitive?

By default, comparison is case-insensitive ("The" and "the" count as duplicates). You can toggle to case-sensitive mode.
Does it remove duplicate lines too?

This tool removes duplicate words within text. To remove duplicate lines, use the Duplicate Line Remover tool.
Remove Duplicate Words —Delete Repeated Words from Text Free

Case-insensitive Strip punctuation before comparing
Result
  <section class="ds-seo-section">
    <h2 class="ds-seo-section__title">What is Remove Duplicate Words?</h2>
    <p>Remove Duplicate Words tool scans your text and removes all repeated words, keeping only the first occurrence of each word. Useful for cleaning keyword lists, tag clouds, and deduplicated content.</p>
  </section>
  <section class="ds-seo-section"><h2 class="ds-seo-section__title">How to Use Remove Duplicate Words</h2><ol><li>Paste your text into the input box.</li><li>Choose case sensitivity and punctuation options.</li><li>Click Remove Duplicates —the first occurrence of each word is kept.</li><li>Copy the result or clear to start over.</li></ol></section>
  </div>
  <div class="ds-related-tools"><h2 class="ds-related-title">Related Tools</h2><div class="ds-related-grid"><a href="duplicate-line-remover.html" class="ds-related-card"><span class="ds-related-icon">🧹</span><div><div class="ds-related-name">Duplicate Line Remover</div><div class="ds-related-desc">Remove duplicate lines from text</div></div></a><a href="list-deduplicator.html" class="ds-related-card"><span class="ds-related-icon">📋</span><div><div class="ds-related-name">List Deduplicator</div><div class="ds-related-desc">Deduplicate list items</div></div></a><a href="text-cleaner.html" class="ds-related-card"><span class="ds-related-icon">🧹</span><div><div class="ds-related-name">Text Cleaner</div><div class="ds-related-desc">Remove unwanted characters from text</div></div></a></div></div>
  <details class="ds-seo-more"><summary class="ds-seo-more__toggle"><span>Learn More</span><span class="ds-seo-more__arrow">▾</span></summary><div class="ds-seo-more__body"><details class="ds-seo-collapse"><summary>Common Use Cases</summary><div class="ds-seo-collapse__body"><ul><li>Clean up keyword lists with repeated terms</li><li>Remove accidental word repetitions in drafts</li><li>Deduplicate tag clouds or word lists</li></ul></div></details><details class="ds-seo-collapse"><summary>Frequently Asked Questions</summary><div class="ds-seo-collapse__body"><div class="ds-seo-faq-item"><strong>Does it preserve word order?</strong><p>Yes. The first occurrence of each word is kept, preserving original order.</p></div><div class="ds-seo-faq-item"><strong>Is my text sent to a server?</strong><p>No. Everything runs in your browser.</p></div></div></details></div></details>
  <!-- AUTO-SEO-SECTIONS:END -->
</div>
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  const text=inputText.value;
  const tokens=text.match(/\S+|\s+/g)||[];
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    let key=trimPunct.checked?tok.replace(/[^\w]/g,''):tok;
    if(caseInsensitive.checked)key=key.toLowerCase();
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  const orig=(text.match(/\S+/g)||[]).length;
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</script>
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