Check whether two versions match
The report opens with a field named identical. It is true when the text of every page is the same in both files and false as soon as one page differs. The changed_pages number tells you how many pages to look at.
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Compare PDFs
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Or start from a blank IRS form
Browse all IRS forms →- You add
- One PDF
- You set
- A link to the other PDF
- You get
- A JSON report of text changes
Comparing two PDFs means finding what changed between two versions of a document. This tool compares their text. You add one PDF, paste a direct link to the second in Other PDF URL, and run the job. indox reads the text of every page in both files, matches page 1 with page 1, page 2 with page 2 and so on, and lists the lines that were added or removed on each page. The result is a JSON report you download, not a marked-up PDF. The file you upload is treated as the original and the linked file as the version it is compared against. One comparison runs without an account.
What can you do when you compare two PDFs?
See added and removed lines per page
Each changed page carries two lists. The added list holds the lines found only in the linked PDF, and the removed list holds the lines found only in the PDF you uploaded. Pages with the same text are marked as not changed.
Spot a difference in length
base_pages is the page count of your upload and compared_pages is the page count of the linked file. Extra pages in the longer version are compared with nothing, so their text lands in a single list.
Use the report in your own tools
JSON opens in a text editor or a browser, and a script can read it too. That makes the output practical for an automated check of documents your software generates.
What comparing keeps and changes
Stays the same
- Both PDFs. Neither one is edited.
- The files on your device.
Changes
- You get one JSON report and no highlighted or merged PDF.
- Text is read from each page and compared line by line. A line must match exactly.
- Pages are paired by number, so page 3 of your upload meets page 3 of the linked file.
- Images, fonts, colors and layout are not part of the comparison.
- Each added and removed list stops at 500 lines per page.
How to compare two PDFs in 3 steps
Add the original PDF
Drop the older version on the upload box, or select Choose file to pick it.
Paste a link to the other PDF
Put the address of the newer version in Other PDF URL. It has to be a direct link to the PDF file itself.
Run the comparison and download the report
Select Run Compare PDFs. When the job is done, select Download to save the JSON report, then open it in a text editor.
Why compare PDFs with indox?
The compare page asks for two things, a PDF and a link, and returns one structured answer. The report says whether the two texts are identical, counts the changed pages and lists the exact lines behind each change, so you can go straight to the pages that matter. A single comparison runs without an account. The PDF you upload is sent over HTTPS, and files on the free tier are deleted automatically within 24 hours after the comparison finishes. This page is also plain about scope: the tool compares text and nothing else.
- One true or false answer for the whole document
- Added and removed lines listed page by page
- A JSON report for people and scripts
- One comparison without an account
- HTTPS for the PDF you upload
What are the limits when you compare PDFs?
- Size
- The free tier has a file size limit. Signing in raises it, and paid plans raise it further.
- Formats
- This tool works on PDF files. To change a file's type, use the PDF converter.
- Privacy
- Files are encrypted in transit and processed on indox infrastructure.
- Deletion
- Free-tier files are deleted automatically within 24 hours after the job finishes. Signed-in output stays in your history for your plan's retention period.
Limits worth knowing
- The second PDF comes from a link. The page has one upload box, so the other file must sit at a public http or https address that returns the PDF without a sign-in.
- Only text is compared. Images, fonts, colors and layout are ignored, and a scanned page with no text layer reads as empty, so two different scans can be reported as identical.
- Pages are matched by number. A page inserted near the start pushes every later page out of step, and all of them show as changed.
- The result is raw JSON, with no side by side view and no highlighted PDF to read.
- The compare page has no password box. Take the open password off with Unlock PDF before you compare a protected file.
When the report is not what you expected
| What you see | Why | What to do |
|---|---|---|
| Every page after an insertion shows as changed | Pages are paired by number, so one extra page shifts everything behind it | Take out the extra page, or compare matching ranges cut with Extract Pages. |
| The report says identical, but the files differ | Only text is compared, or the pages are scans with no text layer | Run OCR PDF on both files, then compare again. |
| One changed word shows a whole line | Lines are compared as a whole | Read the removed and added line side by side. |
| The job fails on the second file | The link must return the PDF itself from a public address, without a sign-in | Open the link in a private window. It should download the PDF. |
| The page asks for a password | The page has no password field | Remove it with Unlock PDF first. |
What do the free and paid plans add?
Free
- All converters
- Daily credit refresh
- Email support
Basic
- Access to all features
- AI Extract
- Priority conversions
- Email support
Highest priority
Premium
- Everything in Basic
- Highest priority queue
- Larger file limits
- Priority support
Pay-As-You-Go
- No subscription
- Credits never expire
- Opt-in auto-refill
- Access to all features
What else can you do with a PDF?
Who compares PDFs?
Contract and legal reviewers
A counterparty sends back a revised agreement as a PDF. The report lists the lines that changed, so you read those clauses first.
Editors and technical writers
Two exports of the same manual should differ only where you edited. A comparison shows each page that changed and the wording on it.
Developers who generate PDFs
An invoice or report template is rebuilt after a code change. The identical field gives a simple pass or fail check against a known good file.
When to compare PDFs, and when to pick another tool
- Checking which clauses changed between two drafts of a contract.
- Confirming that a reissued policy or price list has the same wording as the last one.
- Verifying that a regenerated report still produces the expected text.
- Finding the edited pages in a long manual before a review meeting.
- Both files are scans with no text layer. Run OCR PDF on each one first, because the comparison reads text and nothing else.
Where can I read more?
Sources
- Extract Text from a PDFpypdf documentation
- difflib.unified_diffPython documentation
Facts checked on October 16, 2026
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Compare PDFs FAQs
How do I give the tool the second PDF?
Paste a direct link to it in Other PDF URL. The upload box takes one file, so the second PDF has to be online at an address indox can reach without signing in.
Which file counts as the original?
The PDF you upload. Lines that exist only in the linked file are listed as added, and lines that exist only in your upload are listed as removed.
What is in the report?
A JSON file with identical, base_pages, compared_pages, changed_pages and a pages list. Each entry in the list has the page number, a changed flag and, for changed pages, the added and removed lines.
Does the comparison include images and formatting?
No. It reads the text of each page and ignores pictures, fonts, colors and layout. A change that leaves the words the same will not appear in the report.
Can I compare scanned PDFs?
Only after OCR. A scan without a text layer has no text to read, so its pages come out empty. Run OCR PDF on both files before you compare them.
Why are all pages after an insertion marked as changed?
Pages are paired by number. One extra page early in a version shifts everything behind it, and each shifted page is then compared with a different page.
Can I compare PDFs without signing in?
Yes. Compare PDFs is on the free tier, and a single comparison runs without an account.
Are the two PDFs stored after the comparison?
On the free tier, the PDF you uploaded and the comparison report are deleted automatically within 24 hours after the job finishes. The upload and the download both use HTTPS.