What Thiruttham checks today, what is in progress, and what it does not do
Thiruttham is a Tamil spelling and grammar checker for formal written Tamil, as a Chrome extension and a web editor. In short:
- Each correction shows its reason and whether a fixed rule or the AI made it (on the Free plan, AI corrections past the daily limit stay locked).
- Nothing changes until you accept it. Words you add to your protected list, such as names, are never changed (the list needs a sign-in); a name that is not on the list can still get a suggestion, which you can reject.
- The fixed rules are free, run in your browser and need no account.
- With the Chrome extension it works in Gmail, the WordPress and Blogger editors and other web text boxes (not every site has been tested, and not Google Docs yet). The web editor works on any device.
- Your text is not used to train AI: our AI provider's terms exclude training on it.
- Both the fixed rules and the AI can be wrong or miss a mistake, so a text with no suggestions can still contain mistakes. You can report any wrong correction.
Below is each check, what it covers today and what is in progress. Thiruttham does not give a figure for how often it is right. The tables use these words:
- "Yes": on today.
- "Yes, listed cases": on today, only for the cases in its note.
- "Yes, when confident": the AI shows an edit only when it is confident; it can miss a mistake, and it can be wrong.
- "In progress": being built or rebuilt; it does not run today.
- "Not offered": Thiruttham does not do this.
Fixed rules: free, in your browser, no account
Consonant doubling (ottru) is checked only in the cases listed below (and, on Pro and the trial, by the AI step for other words ending in ஐ or கு), so a text with no suggestions can still contain mistakes. Each fixed-rule line that is on is checked against the checker's code with an example sentence whenever the site is built.
| Feature | Today | Note |
|---|---|---|
| Consonant doubling (ottru) after அந்த, இந்த and எந்த | Yes | The next hard consonant doubles. |
| Doubling after ஆக and என, and after a short list of similar verb forms | Yes, listed cases | The next hard consonant doubles. |
| Doubling after the object ending ஐ | Yes, listed cases | For the listed forms of the object ending, and not after a bare noun. The pronoun forms and several other forms are not covered. |
| Doubling after the dative ending கு | Yes, listed cases | For the pronoun forms and the listed dative endings. Other endings are not covered. |
| Doubling after அனைத்து | Yes | The next hard consonant doubles. |
| Doubling after certain verb forms, including the infinitive | Yes, listed cases | Closed lists of forms only, and the passive participle (the form that means "having been done"). A village or place name that ends like one can rarely be taken for a verb form. |
| A pulli (ottru) missing or typed in the wrong place in a common word | Yes, listed cases | A closed list built from the most frequent Tamil words, so a typing slip in a rarer word is not caught. A name that looks like a typing slip can rarely be flagged by mistake. |
| A doubling written by mistake after certain verb forms | Yes, listed cases | The extra consonant is removed, for the listed forms only. |
| Standard spellings | Yes, listed cases | A short list of common misspellings, each with its standard form. It is a list, not a dictionary. |
| Written forms of spoken words | Yes, listed cases | A list of 45 common spoken words and endings and their written forms. It is on by default and you can turn it off; if you write dialogue, you may want it off. |
| More cases of consonant doubling | In progress | Cases not listed above are not checked today, so a text with no suggestions can still contain mistakes. More cases are being added. |
| Doubling after எட்டு and பத்து | In progress | Being rebuilt. The first version gave too many wrong suggestions in testing, for example on names that contain பத்து, so it does not run today. |
| Words that wrongly begin with ண or ன | In progress | Being rebuilt. The first version gave too many wrong suggestions in testing, so it does not run today. |
AI-assisted check: after you sign in
These depend on what the sentence means, so a fixed rule cannot decide them. The AI proposes small edits, each an exact piece of your text and its replacement, and shows only the ones it is confident about.
| Feature | Today | Note |
|---|---|---|
| Similar-sounding letters: ர and ற, ல and ள and ழ, ந and ண and ன | Yes, when confident | The AI proposes an edit only when it is confident, so it can miss a mistake, and it can be wrong. |
| Agreement between subject and verb, in gender and in number | Yes, when confident | The same: only confident edits are shown, and it can be wrong. |
| Written forms of spoken words beyond the short list | Yes, when confident | The AI proposes a written form only when it is confident. |
| Doubling after other words that end in ஐ or கு (Pro and the 7-day trial) | Yes, when confident | A second AI step answers yes or no for each case the fixed rules cannot decide, and a suggestion is shown only on a yes. It can miss a case and it can be wrong. |
| The glide letters that join words (one kind of sandhi) | In progress | Being rebuilt. The AI's first suggestions were not reliable enough, so it does not run today. |
| Deciding whether a word needs the object ending ஐ or the dative ending கு | In progress | Being built. It does not run today: no suggestion is made either way. |
Typing and where it works
| Feature | Available | Note |
|---|---|---|
| Typing Tamil with English letters (Tanglish) | Yes | In beta. You choose from a list of spellings; the first is not always the one you want. |
| Inside Gmail, the WordPress and Blogger editors and most web text boxes | Yes | With the Chrome extension. It stays out of search and sign-in boxes, and you can turn it off for any site. |
| The web editor | Yes | Works in any modern browser, including on a phone. |
| The fixed rules offline | Yes | They run in your browser and need no account. |
| A personal list of protected words | Yes | After you sign in. Words on it, such as names, are never changed. |
| Opening a .docx file in the editor | Yes | On the paid plans and the 7-day trial. A .txt file opens on any plan. |
In progress
These are being built. None of them works today, and there is no date for them yet; each line says what to do until it does. Pay for what works today: the 7-day trial lets you check that first. This list was last reviewed on 4 November 2026.
| Feature | Status | Note |
|---|---|---|
| Rewriting a whole sentence, or changing how formal a text sounds | In progress | Not today. Today it proposes small corrections to the text you wrote, and nothing changes until you accept it. |
| Reading handwriting or images (OCR) | In progress | Today, type or paste the text instead. |
| Voice typing | In progress | Today, type, or use Tamil typing with English letters. |
| Google Docs | In progress | Google Docs is not supported yet. Today, paste your text into the web editor to check it, then copy it back. |
| A Microsoft Word add-in | In progress | Today, paste your text into the editor, then copy it back, or open a .docx there on a paid plan. |
| Checking a PDF directly | In progress | Today, copy the text out of the PDF and paste it in. |
What Thiruttham does not do
| Feature | Today | Note |
|---|---|---|
| Translating or drafting new text | Not offered | It only corrects text you wrote. |
| The extension on a phone, in Firefox or in Safari | Not offered | It works in Chrome and other Chromium browsers on a computer. On a phone, use the web editor. |
What each part sends
- A rule check runs in your browser and sends nothing.
- Tamil typing converts in your browser and sends nothing.
- An AI-assisted check sends the sentences you check to our server and to a language model provider whose terms exclude training on your text and keeping it. Each checked sentence is kept encrypted for up to 30 days so that a repeat check is fast; no person reads it.
Free and Pro
The fixed rule checks are free and unlimited. With a free account you get 5 AI-assisted corrections a day, and the AI reads the first 500 words of a text. You can start a 7-day trial of Pro yourself, once, with no payment needed. Pro is ₹299 a month or ₹2,799 a year; the pricing page has the details.
Both the rules and the AI can be wrong. A rule can flag a name or an unusual word, and the AI can propose changing a word that is correct. Nothing changes until you accept it, and words on your protected list are never changed. You can dismiss any suggestion or report a wrong correction.
Does Thiruttham check sandhi?
It checks doubling (ottru): the fixed-rule cases listed above and, on Pro and the 7-day trial, an AI step for other words ending in ஐ or கு. Other kinds of sandhi, including the glide letters that join words, are in progress and are not checked today.
Does Thiruttham check grammar?
Yes, for the cases listed above. The fixed rules cover the listed doubling rules, a short list of standard spellings and a list of spoken words. The AI-assisted check, after sign-in, looks at similar-sounding letters and agreement between subject and verb, shows only edits it is confident about, and can miss a mistake or be wrong.
Does Thiruttham have OCR or voice typing?
Not yet. Both are in progress. Today it checks text you type or paste.
Does Thiruttham rewrite or translate my text?
No. Today it proposes small corrections to the text you wrote, and nothing changes until you accept it. Rewriting a whole sentence and changing the tone are in progress; translating is not offered.
Does it work offline?
The fixed rules do: they run in your browser and need no account. The AI-assisted check needs a connection and a sign-in.