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Privacy Policy

Last updated: September 30, 2026

The Short Version

OfflineTTS is designed so that speech synthesis and transcription inference run in your browser. The application does not upload your source audio or generated audio to OfflineTTS for processing. One content exception is documented below: non-English Kokoro sends the text you enter to api.offlinetts.com for phonemization before your browser generates audio. The website also uses hosting, analytics, model-delivery, and optional affiliate services that receive ordinary web requests under their own policies.

Data We Collect

OfflineTTS does not currently require an account, payment profile, or API key. The browser application is not designed to send English TTS text, STT recordings, generated audio, or exported files to OfflineTTS for speech inference. Files you select are processed in the browser unless a tool explicitly describes another data path.

We load Google Analytics (GA4) only after you allow optional analytics, or when a saved allowance is present. Before that choice the GA4 script is not requested. Allowed measurement can include page paths, device and browser information, approximate location derived from IP address, and interaction metadata. We strip query strings and fragments from the page URL and referrer supplied to GA4. Speech text, recordings, and generated audio are not included in our custom analytics events. Microsoft Clarity session replay has been removed.

Phonemization (Non-English TTS)

Kokoro's browser library natively supports English phonemization — English voices work fully offline. For Japanese, Chinese, Spanish, French, Hindi, Italian, and Portuguese, the current Kokoro integration uses the OfflineTTS phonemization API. This is an implementation choice, not a claim that browser phonemization is impossible.

  • What is sent: Your plain text is sent to api.offlinetts.com and converted to a phoneme string
  • What is received: A phoneme string returned to your browser, where audio synthesis happens locally
  • What the application does not submit to this endpoint: Source audio, generated audio, account details, or payment information
  • Retention: The phonemization application is configured not to persist submitted text as application content; infrastructure may still process standard security and request metadata
  • English Kokoro: Does not use this phonemization endpoint after required assets are available

How It Works

  • TTS models and STT models (approximately 120–590MB for Whisper Tiny through Small) are downloaded to your browser on first use and cached in IndexedDB
  • All speech generation and transcription happens on your device using WebGPU or WebAssembly
  • English Kokoro does not send text to the phonemization endpoint after the model and application assets are available
  • Non-English Kokoro voices send plain text to our phonemization server, which returns IPA phoneme strings (pronunciation data). Audio synthesis still happens locally
  • TTS audio is generated in-memory and can be downloaded as WAV files
  • STT audio is decoded in a background Web Worker and transcribed locally
  • The OfflineTTS application does not upload source or generated audio for speech inference

Model Files

AI model files (TTS and STT) are served from Cloudflare R2 (CDN) and Hugging Face. When you load a tool, your browser downloads the required model files. A model host receives a normal HTTPS request and may process IP address, request headers, timestamps, and security logs under its policy. Model downloads are not the site's only network activity: the page itself, allowed optional analytics, advertisements on eligible public content pages, fonts or other static assets, non-English Kokoro phonemization, and links you choose to follow can also create requests.

Cookies and Browser Storage

GA4 may use measurement cookies after you allow analytics. You can decline it or withdraw via “Analytics settings” in the footer; withdrawal disables further GA4 measurement in this browser. Your saved choice uses local storage. Advertising choices are separate and use Google’s consent message where applicable. OfflineTTS uses IndexedDB, OPFS, Cache Storage, and local storage for models, worker communication, and tool preferences. Local tool storage stays in that browser profile until it expires, the application replaces it, or you clear it. The homepage hands a draft to the advanced workspace using session storage in the same tab. That handoff is consumed once and is rejected after five minutes; unconsumed storage may remain until that tab closes or site data is cleared. If storage is unavailable, the link stays on the homepage and displays a message instead of putting the draft into a URL.

Delete Local Data

To remove cached models, tool preferences, and other local application data, use your browser's site-data controls for offlinetts.com. Clearing only normal history may not remove IndexedDB, Cache Storage, or OPFS, so choose the control that deletes site storage. The next visit may need to download models again. Audio, transcripts, subtitles, or documents you exported are ordinary files on your device and must be deleted through your operating system or file manager.

You can limit analytics with browser privacy settings, content blockers, provider opt-outs, or applicable consent choices. The Google Analytics opt-out link is provided below. Those controls do not delete exported files and may not erase data already handled by a third party; consult that provider's policy for its request process.

Third-Party Services

We use the following third-party services:

  • Google Analytics (GA4): When you allow analytics, we use GA4 for aggregate site measurement such as pages visited, referrals, device type, and interaction events. Google handles that data under its policies. You can use the Google Analytics Opt-out Browser Add-on.
  • Google AdSense & Advertising Partners: Advertising is deployment-dependent: Google AdSense, optional third-party native ads, or no ads. The two advertising modes are mutually exclusive. Tool workspaces, private reader states, voice detail pages, and noindex pages do not load our advertising integrations. Popunder advertising has been removed. Third-party vendors, including Google, use cookies and similar technologies to serve ads based on prior visits to this website or other websites. Google's use of advertising cookies enables it and its partners to serve ads to users based on their visits to OfflineTTS and other sites across the Internet.
  • Cloudflare: The site and some model assets use Cloudflare infrastructure, which processes normal network and security information such as IP addresses, requested URLs, headers, and timestamps.
  • Hugging Face and other model sources: A browser may request model or runtime assets from an upstream host. That host handles the network request under its own policy.

New homepage workspace links contain no draft text. Legacy links containing a text query are cleaned before our third-party scripts initialize; the initial request for such an old URL still reaches the hosting infrastructure. Avoid putting confidential content into a URL, page title, support message, or another field that a website service could ordinarily observe. The non-English Kokoro content path is the separate phonemization exception above.

Advertising & Cookie Opt-Out

In AdSense mode, the Google advertising loader is paused before ad requests. Google’s certified consent management message must be published in the AdSense account. Where GDPR applies, requests remain paused unless its signal permits Google and storage purpose consent; without a valid signal, our integration stays paused. Personalized requests additionally require the relevant personalization consent. Other consent and eligibility checks are handled by Google’s advertising tag. The paused loader still makes a network request and may read existing Google cookies. Eligible visitors can reopen the message using “Ad privacy settings” in the footer. Our optional analytics notice is separate and is not presented as a Google-certified CMP.

In the separate native-ad mode, a marked sponsored slot identifies Adsterra and links to its privacy policy. Its provider script loads only when you choose “Load sponsored content.” That action allows the external provider to receive a normal web request and apply its own storage policies. Popunder ads are not supported.

  • Personalized Advertising Opt-Out: You may opt out of personalized advertising from Google by visiting Google Ads Settings.
  • Industry-Wide Opt-Out: You can also opt out of third-party vendor cookies for personalized advertising by visiting AboutAds.info Choices or the Network Advertising Initiative opt-out page at Network Advertising Initiative.
  • Speech content boundary: Our application does not put typed text, recordings, or generated audio into advertising or analytics events. Non-English Kokoro has the documented phonemization exception. Do not put confidential material into a URL or send it in a support request.

Affiliate Links

Some clearly marked links are affiliate links. Clicking one leaves OfflineTTS and allows the destination or affiliate network to receive the normal web request and use attribution cookies or similar technology under its own policy. Any account, content, purchase, or payment information you provide after leaving the site is handled by that third party. See the Affiliate & Trademark Disclosure for where paid links appear and how recommendations are reviewed.

Changes

If data handling changes materially, we will update this page and its “Last updated” date. Our product goal is to minimize server handling of speech content, keep audio inference in the browser, and document exceptions plainly enough that you can make an informed choice.

Contact

Questions about privacy? Contact us at contact@offlinetts.com.