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formeo merged 1 commit into from
Oct 22, 2026
Merged

Joiner and Speed Changer copy for real queries; guard the TTS "-ai" niche #21

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8 changes: 8 additions & 0 deletions .github/workflows/seo-check.yml
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Expand Up @@ -16,3 +16,11 @@ jobs:
- run: pip install beautifulsoup4
- name: FAQPage JSON-LD matches the visible FAQ
run: python3 scripts/seo_sync.py --check
- name: Text to Speech pages don't use the word "AI"
# People searching "text to speech -ai" exclude pages containing the word, and they find this page in the
# top 10 (Search Console, Oct 2026). One "AI" anywhere on the page would drop it from those results.
run: |
if grep -nwi 'ai' text-to-speech/index.html zh/text-to-speech/index.html; then
echo '::error::The word "AI" appeared on a Text to Speech page; see the comment in seo-check.yml.'
exit 1
fi
22 changes: 20 additions & 2 deletions audio-joiner/index.html
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Expand Up @@ -54,6 +54,22 @@
"text": "Add the MP3 files, arrange them in order, optionally set a crossfade, then click Merge & Download. You get one MP3 or WAV file, made in your browser."
}
},
{
"@type": "Question",
"name": "How do I combine two audio files?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Add both files, put them in the order you want and click Merge & Download: the second file plays right after the first. A crossfade blends the end of the first into the start of the second."
}
},
{
"@type": "Question",
"name": "Can I overlay two audio files so they play at the same time?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Not yet. Audio Joiner plays files one after another; mixing tracks on top of each other, such as a voice over music, is not available yet."
}
},
{
"@type": "Question",
"name": "Can I merge different formats?",
Expand Down Expand Up @@ -223,15 +239,15 @@ <h1>Merge Audio Files</h1>

<section class="seo-content">
<h2>Merge MP3 and other audio files online</h2>
<p>Add your files, put them in order and download one file. Audio Joiner runs entirely in your browser: the files are decoded, joined and encoded on your device, so nothing is uploaded, and there is no size quota and no waiting in line.</p>
<p>Audio Joiner is a free online audio merger and MP3 joiner: add your files, put them in order and download one file. It runs entirely in your browser: the files are decoded, joined and encoded on your device, so nothing is uploaded, and there is no size quota and no waiting in line.</p>
<h3>How to merge audio files</h3>
<ol>
<li>Drop your files on the box above, or click to choose them. You can add more later with “Add more files”.</li>
<li>Drag the tracks into the order you want, or use the arrows.</li>
<li>Optionally set a crossfade of up to 3 seconds for a smooth transition. Leave it at 0 for a straight cut.</li>
<li>Click “Merge &amp; Download” and save the result as MP3 (192 kbps) or WAV.</li>
</ol>
<h3>What you can merge</h3>
<h3>Combine audio files of any format</h3>
<p>MP3, WAV, M4A/AAC, FLAC, OGG and Opus files, mixed in any order: anything your browser can play. Voice messages saved from WhatsApp or Telegram (.opus, .ogg) work in browsers that play Opus, such as Chrome, Edge and Firefox. Mono and stereo files can be mixed, and files with different sample rates are brought to one rate automatically.</p>
<h3>Common uses</h3>
<ul>
Expand All @@ -251,6 +267,8 @@ <h3>Limits</h3>
<section class="faq">
<h2>Frequently Asked Questions</h2>
<div class="faq-item"><div class="faq-q">How do I merge MP3 files into one?</div><div class="faq-a">Add the MP3 files, arrange them in order, optionally set a crossfade, then click Merge &amp; Download. You get one MP3 or WAV file, made in your browser.</div></div>
<div class="faq-item"><div class="faq-q">How do I combine two audio files?</div><div class="faq-a">Add both files, put them in the order you want and click Merge &amp; Download: the second file plays right after the first. A crossfade blends the end of the first into the start of the second.</div></div>
<div class="faq-item"><div class="faq-q">Can I overlay two audio files so they play at the same time?</div><div class="faq-a">Not yet. Audio Joiner plays files one after another; mixing tracks on top of each other, such as a voice over music, is not available yet.</div></div>
<div class="faq-item"><div class="faq-q">Can I merge different formats?</div><div class="faq-a">Yes. MP3, WAV, M4A, FLAC, OGG and Opus can be mixed in one merge. Each file is decoded by your browser and the result is saved as MP3 or WAV.</div></div>
<div class="faq-item"><div class="faq-q">Can I combine WhatsApp or Telegram voice messages?</div><div class="faq-a">Yes. Save the voice messages from the chat (they are .opus or .ogg files) and add them here. Chrome, Edge and Firefox play these files; some older Safari versions do not.</div></div>
<div class="faq-item"><div class="faq-q">Does merging reduce audio quality?</div><div class="faq-a">Saving as WAV keeps the decoded audio unchanged. Saving as MP3 re-encodes it at 192 kbps, which sounds the same as the original for speech and most music.</div></div>
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79 changes: 54 additions & 25 deletions audio-speed-changer/index.html
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Expand Up @@ -14,30 +14,30 @@
gtag('config', 'G-62ZJNZFRES');
</script>

<title>Audio Speed Changer — Slow Down / Speed Up | AudioTools.dev</title>
<meta name="description" content="Change audio playback speed online for free. Slow down or speed up MP3, WAV files without pitch change. No upload, runs in browser.">
<meta name="keywords" content="audio speed changer, slow down audio, speed up mp3, change audio speed online, audio tempo changer, slow down music, speed up audio file">
<title>Audio Speed Changer &amp; Slow Downer Online | AudioTools.dev</title>
<meta name="description" content="Slow down or speed up MP3, M4A or WAV from 0.25x to 4x without changing pitch: learn a song, practise a language or listen faster. Free, no upload.">
<meta name="keywords" content="audio speed changer, audio slow downer, slow down audio, slow down mp3, slow down m4a, slow down wav, slow down a song, speed up audio, change speed without changing pitch">
<link rel="canonical" href="https://audiotools.dev/audio-speed-changer/">
<meta property="og:type" content="website">
<meta property="og:site_name" content="AudioTools.dev">
<meta property="og:locale" content="en_US">
<meta property="og:url" content="https://audiotools.dev/audio-speed-changer/">
<meta property="og:title" content="Audio Speed Changer — Slow Down / Speed Up | AudioTools">
<meta property="og:description" content="Change audio playback speed online for free. Slow down or speed up MP3, WAV files without pitch change. No upload, runs in browser.">
<meta property="og:title" content="Audio Speed Changer &amp; Slow Downer Online">
<meta property="og:description" content="Slow down or speed up MP3, M4A or WAV from 0.25x to 4x without changing pitch: learn a song, practise a language or listen faster. Free, no upload.">
<meta property="og:image" content="https://audiotools.dev/og/audio-speed-changer.png">
<meta property="og:image:width" content="1200">
<meta property="og:image:height" content="630">
<meta property="og:image:alt" content="Audio Speed Changer — Slow Down / Speed Up | AudioTools">
<meta property="og:image:alt" content="Audio Speed Changer &amp; Slow Downer Online">
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:title" content="Audio Speed Changer — Slow Down / Speed Up | AudioTools">
<meta name="twitter:description" content="Change audio playback speed online for free. Slow down or speed up MP3, WAV files without pitch change. No upload, runs in browser.">
<meta name="twitter:title" content="Audio Speed Changer &amp; Slow Downer Online">
<meta name="twitter:description" content="Slow down or speed up MP3, M4A or WAV from 0.25x to 4x without changing pitch: learn a song, practise a language or listen faster. Free, no upload.">
<meta name="twitter:image" content="https://audiotools.dev/og/audio-speed-changer.png">
<meta name="robots" content="index, follow, max-snippet:-1, max-image-preview:large">
<link rel="icon" type="image/svg+xml" href="/favicon.svg">
<link rel="icon" type="image/x-icon" href="/favicon.ico">
<link rel="apple-touch-icon" href="/apple-touch-icon.png">
<script type="application/ld+json">
{"@context":"https://schema.org","@type":"WebApplication","name":"Audio Speed Changer — AudioTools.dev","url":"https://audiotools.dev/audio-speed-changer/","description":"Change audio playback speed online for free. Slow down or speed up MP3, WAV files without pitch change. No upload, runs in browser.","applicationCategory":"MultimediaApplication","operatingSystem":"Any","isAccessibleForFree":true,"offers":{"@type":"Offer","price":"0","priceCurrency":"USD"}}
{"@context":"https://schema.org","@type":"WebApplication","name":"Audio Speed Changer — AudioTools.dev","url":"https://audiotools.dev/audio-speed-changer/","description":"Slow down or speed up MP3, M4A or WAV from 0.25x to 4x without changing pitch: learn a song, practise a language or listen faster. Free, no upload.","applicationCategory":"MultimediaApplication","operatingSystem":"Any","isAccessibleForFree":true,"offers":{"@type":"Offer","price":"0","priceCurrency":"USD"}}
</script>
<script type="application/ld+json">
{
Expand All @@ -46,18 +46,34 @@
"mainEntity": [
{
"@type": "Question",
"name": "Can I change speed without pitch change?",
"name": "How do I slow down an audio file without changing the pitch?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Yes. The tool uses WSOLA time-stretching to preserve original pitch while adjusting playback speed from 0.25x to 4x."
"text": "Drop the file here, choose a speed below 1x (for example 0.75x) and click Apply & Process. WSOLA time-stretching keeps the original pitch; download the result as MP3 or WAV."
}
},
{
"@type": "Question",
"name": "What formats are supported?",
"name": "Can I slow down an M4A or WAV file?",
"acceptedAnswer": {
"@type": "Answer",
"text": "MP3, WAV, FLAC, OGG, AAC, M4A, WebM. Output is saved as MP3 or WAV."
"text": "Yes. MP3, M4A/AAC, WAV, FLAC, OGG and WebM all work. The result is saved as MP3 or WAV."
}
},
{
"@type": "Question",
"name": "What speed is best for learning a song?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Start at 0.5x–0.75x and raise the speed as the part becomes comfortable. The pitch stays the same, so you can play along in the original key."
}
},
{
"@type": "Question",
"name": "Can I speed up a podcast or voice message?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Yes. Choose 1.25x–2x and download the result. A 60-minute recording takes 40 minutes at 1.5x."
}
},
{
Expand Down Expand Up @@ -145,7 +161,7 @@
<section class="hero">
<svg class="hero-glyph" viewBox="0 0 160 56" aria-hidden="true"><path class="g-ink" d="M4 28 C14 6 24 6 34 28 S54 50 64 28"/><polyline class="g-acc" points="74,28 78,12 82,44 86,12 90,44 94,12 98,44 102,12 106,44 110,12 114,44 118,12 122,44 126,12 130,44 134,12 138,44 142,12 146,44 150,28"/></svg>
<h1>Audio Speed Changer</h1>
<p>Slow down or speed up any audio file — adjust tempo without changing the pitch</p>
<p>Slow down or speed up any audio file — MP3, M4A, WAV — without changing the pitch</p>
</section>

<div class="tool-area">
Expand Down Expand Up @@ -204,21 +220,34 @@ <h1>Audio Speed Changer</h1>
</div>

<section class="seo-content">
<h2>Free Online Audio Speed Changer</h2>
<p>Audio Speed Changer lets you adjust the playback speed of any audio file from 0.25x (4x slower) to 4x faster, while preserving the original pitch. Perfect for language learning, music practice, transcription work, and podcast listening.</p>
<h3>Speed Change with Pitch Preservation</h3>
<p>A naive speed change also alters pitch — making things sound higher when sped up and lower when slowed down. This tool uses a WSOLA (Waveform Similarity Overlap-Add) time-stretching algorithm to change speed while keeping the original pitch, so voices and music sound natural at any speed.</p>
<h3>How It Works</h3>
<p>Drop or select your audio file, choose a speed with the slider or a preset, then click "Apply &amp; Process". The file is decoded with the Web Audio API, time-stretched directly in your browser, and offered for download as MP3 or WAV. Nothing is uploaded to any server.</p>
<h3>Common Use Cases</h3>
<p>Language learning — slow down native speakers to catch every word. Music practice — slow down guitar solos or drum patterns to learn at your pace. Transcription — slow down recordings for accurate typing. Podcasts — speed up to 1.5–2x to listen faster.</p>
<p>Need other edits? Try our <a href="/audio-trimmer/">Audio Trimmer</a>, <a href="/converter/">Audio Converter</a>, <a href="/text-to-speech/">Text to Speech</a>, or <a href="/voice-to-text/">Voice to Text</a>.</p>
<h2>Slow down or speed up audio without changing pitch</h2>
<p>Audio Speed Changer is an online audio slow downer and speed changer. It plays any recording from 0.25x (four times slower) to 4x faster and keeps the original pitch, so a slowed-down song stays in its key and a sped-up voice does not turn into a chipmunk. It runs in your browser: nothing is uploaded.</p>
<h3>How to slow down an audio file</h3>
<ol>
<li>Drop an MP3, M4A, WAV or other audio file on the box above.</li>
<li>Pick a preset (0.5x, 0.75x, 1.25x, 1.5x, 2x) or set any speed from 0.25x to 4x with the slider.</li>
<li>Click “Apply &amp; Process” and listen to the result.</li>
<li>Download it as MP3 or WAV.</li>
</ol>
<h3>Slow down a song to learn it</h3>
<p>Guitar solos, piano parts and drum fills are easier to learn at 0.5x–0.75x. Because the pitch stays the same, you can play along in the original key. To loop one passage, cut it out first with the <a href="/audio-trimmer/">audio trimmer</a>, then slow it down here.</p>
<h3>Slow down speech for language learning and transcription</h3>
<p>At 0.75x, native speakers become much easier to follow without sounding unnatural. For typing up an interview or a lecture by hand, 0.5x–0.75x lets you keep up with the speaker.</p>
<h3>Speed up podcasts, lectures and voice messages</h3>
<p>At 1.5x, a 60-minute lecture takes 40 minutes; at 2x, 30. The result is a shorter file you can keep and play anywhere, not just a faster player setting.</p>
<h3>Pitch stays put</h3>
<p>A naive speed change also shifts pitch: higher when sped up, lower when slowed down. This tool uses WSOLA (Waveform Similarity Overlap-Add) time-stretching, which changes the tempo while keeping the original pitch, so voices and instruments sound natural.</p>
<h3>Supported formats</h3>
<p>MP3, M4A/AAC, WAV, FLAC, OGG and WebM: anything your browser can play. The result is saved as MP3 or WAV; for M4A or FLAC, convert it afterwards with the <a href="/converter/">audio converter</a>.</p>
<p>Want the words instead? <a href="/voice-to-text/">Voice to text</a> transcribes a recording on your device. To join several recordings first, use the <a href="/audio-joiner/">audio joiner</a>.</p>
</section>

<section class="faq">
<h2>Frequently Asked Questions</h2>
<div class="faq-item"><div class="faq-q">Can I change speed without pitch change?</div><div class="faq-a">Yes. The tool uses WSOLA time-stretching to preserve original pitch while adjusting playback speed from 0.25x to 4x.</div></div>
<div class="faq-item"><div class="faq-q">What formats are supported?</div><div class="faq-a">MP3, WAV, FLAC, OGG, AAC, M4A, WebM. Output is saved as MP3 or WAV.</div></div>
<div class="faq-item"><div class="faq-q">How do I slow down an audio file without changing the pitch?</div><div class="faq-a">Drop the file here, choose a speed below 1x (for example 0.75x) and click Apply &amp; Process. WSOLA time-stretching keeps the original pitch; download the result as MP3 or WAV.</div></div>
<div class="faq-item"><div class="faq-q">Can I slow down an M4A or WAV file?</div><div class="faq-a">Yes. MP3, M4A/AAC, WAV, FLAC, OGG and WebM all work. The result is saved as MP3 or WAV.</div></div>
<div class="faq-item"><div class="faq-q">What speed is best for learning a song?</div><div class="faq-a">Start at 0.5x–0.75x and raise the speed as the part becomes comfortable. The pitch stays the same, so you can play along in the original key.</div></div>
<div class="faq-item"><div class="faq-q">Can I speed up a podcast or voice message?</div><div class="faq-a">Yes. Choose 1.25x–2x and download the result. A 60-minute recording takes 40 minutes at 1.5x.</div></div>
<div class="faq-item"><div class="faq-q">Is my audio uploaded?</div><div class="faq-a">No. Everything happens in your browser using the Web Audio API.</div></div>
</section>
</div>
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