How to compare a document before and after AI rewriting

An AI rewrite can sound smoother while quietly changing a fact, dropping a qualification, or removing a detail you meant to keep. Reading the new version on its own makes those changes easy to miss.

Compare the original and rewritten text side by side first. TooLab's Text Compare helps you spot wording that was added, removed, or changed, so you can review the edits before using the rewrite.

Compare the original and rewritten text

1. Open Text Compare.
2. Copy the original document's text into one side of the comparison and the AI rewrite into the other. Keep the original unchanged so you can refer back to it.
3. Run the comparison. Look through the marked or listed differences from the beginning, not just the first few lines.
4. Check each substantial change against the original. Pay close attention to names, dates, amounts, instructions, claims, and any sentence that states a requirement or exception.
5. Make any corrections in a separate working copy of the rewrite. Keep both source versions until you have checked and approved the final text.

For a long document, compare it in sections with clear boundaries, such as one heading or a few paragraphs at a time. This makes it easier to understand which change belongs to which point, and reduces the chance that a large block of differences hides a small but important edit.

Choose what to compare

Compare the whole document for a broad review

Use the full text when you want to see the overall scale of the rewrite. This is useful for checking whether the AI kept the same sections and whether it added a new claim or removed a paragraph. A long comparison can be harder to scan, so follow up on any dense area in smaller sections.

Compare one section at a time for careful editing

Section-by-section comparison is usually better when the rewrite is extensive or the document contains precise instructions. Keep the same section in each side. If you compare mismatched paragraphs, the results can make a simple rearrangement look like many separate deletions and additions.

Use clean text when formatting is not the question

A text comparison is for words and characters, not page design. Copying text from a word processor may omit layout details such as fonts, margins, page breaks, and some formatting. If you need to check those, inspect the document itself as well as its text.

What the differences mean

Words or sentences appear as added

The rewrite introduced wording that was not in the original. It may be a helpful clarification, but it may also add a promise, explanation, or factual claim that you did not provide. Verify new claims rather than assuming they are true because they read naturally.

Words or sentences appear as removed

Something in the original is missing from the rewrite. Check whether it was repetitive filler or important context, a limitation, a warning, a source, or an exception. A short phrase such as “in some cases” can change the scope of a statement.

A sentence appears changed in several places

The AI may have paraphrased the sentence, changed its order, or combined it with nearby text. Read the complete sentence in both versions. Compare who is doing the action, what is being claimed, and whether the conditions or timing stayed the same.

There are few or no differences

The texts may be nearly identical, or the rewrite may have changed presentation without changing many words. A text comparison cannot tell you whether the new version is more accurate, clearer, or better suited to its audience. Read it aloud or ask a reader who does not know the original to check for clarity.

Review the rewrite before you use it

1. Check facts and numbers. Verify dates, names, amounts, measurements, links, and quoted material against the source. AI can alter a number or make a cautious statement sound certain.
2. Look for missing context. Check headings, examples, caveats, citations, and details that explain who a statement applies to. A rewrite can preserve the main point while dropping a restriction that matters.
3. Read changed instructions in order. If the document tells someone what to do, confirm that the steps still work and that the AI did not reverse a condition or omit a warning.
4. Check tone and audience. The rewrite may be more formal, more direct, or less personal than you intended. Restore words or examples that make the document sound like you and fit its readers.
5. Proofread the final copy on its own. After making corrections, read the complete revised document from start to finish. Comparison highlights differences, but it does not catch every awkward sentence or prove that the final version is correct.

What a text comparison cannot tell you

A difference is not automatically an error. The AI may have improved a sentence, and a substantial rewrite may preserve the original meaning. The comparison only shows textual changes. It cannot judge whether a claim is true, whether a legal or technical statement is safe to publish, or whether the result meets your requirements.

If the document contains sensitive information, follow your workplace or organization's rules before putting its text into any online tool. For important or high-stakes material, verify the content with the original source or a qualified reviewer, even when the changes look small.