Contract Tamper Detection API
Detect altered contract terms, changed clauses, and post-signing modifications – whether the buyer calls the result a tampered contract or a fake one. Add forensic tamper detection to your contract management or e-signature platform: a single API call flags edited PDFs before execution.
HTPBE? analyzes the structural layer of the PDF file – the layer that records every edit, even invisible ones, including modifications applied after a signature. We don’t inspect holograms, phone photos, or ID biometrics, and we don’t replace e-signature platforms or notarisation services. If your fraud problem is a contract PDF altered after signing or fabricated alongside lifted signature images, we’re the most specific tool for it.
On a contract presented as e-signed, INCONCLUSIVE is a reason for manual review – for example against the copy held by the other party – not proof of tampering.
The problem
Contract fraud survives e-signature workflows
E-signature platforms check that a document was signed, not that it has not been modified since. A common attack: one party signs a contract, the other side opens the PDF in Adobe Acrobat, modifies a clause or payment term, and submits the altered version as the ‘executed’ agreement.
In disputes, the altered contract is presented as legitimate. Without forensic analysis, it is difficult to prove which version was the original and which was modified. Digital signature bypass – where the signature page is preserved but content around it is changed – is especially hard to detect visually.
HTPBE? analyzes the binary structure of the PDF, not its visual content. It detects post-signature modifications with ‘certain’ confidence – the highest verdict level in the system – making it suitable for pre-execution tamper checks and dispute investigation.
Common contract fraud patterns
- Payment terms changed after signature (amount, due date, account)
- Liability clause modified to shift risk
- Signature page preserved, contract body replaced
- Governing law or jurisdiction clause altered
- Delivery obligations or SLA terms changed
- Contract date back-dated to claim priority
What this looks like
Document fraud in 2026 – three concrete patterns
Three real fraud mechanics we catch at the structural PDF layer.
Payment terms changed after signature (amount, due date, account)
Liability clause modified to shift risk
Signature page preserved, contract body replaced
Governing law or jurisdiction clause altered
Delivery obligations or SLA terms changed
Contract date back-dated to claim priority
The detection gap
KYC platforms check the document. HTPBE? checks the file.
Two different checks – both matter.
KYC & identity platforms
Plaid · Persona · Alloy · Jumio
- Is this a real bank statement template?
- Does the account number match the identity?
- Is the document format consistent with the issuing bank?
Detects fake documents. Does not detect edited real documents.
HTPBE? tamper detection API
Structural PDF integrity
- Was this specific PDF file modified after it was generated?
- Does the file carry evidence of editing after export?
- Were digital signatures valid at the time of signing?
What HTPBE? checks
Forensic signals analyzed in every contract
Five layers of analysis run on every request – results in under 3 seconds
Modifications after signature
The highest-confidence signal: content added to a digitally signed contract. HTPBE? returns ‘certain’ confidence when it detects changes that were appended after a valid signature was applied.
Signature removal detection
A signature page can be stripped from a contract and the document re-circulated. HTPBE? detects structural evidence of removed signature blocks, also flagged at ‘certain’ confidence.
Post-generation edits
HTPBE? detects contracts that were edited and saved again after they were generated – structural evidence that the file is no longer the original.
Dates that disagree
HTPBE? flags a modification date that differs from the declared creation date, and timestamp records inside the file that contradict each other – evidence the contract was changed after it was produced.
Online PDF editor traces
A contract processed by an online PDF editing service after it was issued is not passed as an untouched original.
Rebuilt contracts
HTPBE? flags a contract that was reconstructed as a new file rather than produced as the original – structural evidence of post-generation editing.
Share with engineering
Wire this into your intake pipeline in under a day
Two API calls – one POST to submit the PDF, one GET to retrieve the verdict. Forward this page to your engineering team; the full API reference, quotas, and copy-paste examples in cURL, JavaScript, Python, PHP, Go, and Ruby are one click away.
Pricing
Self-serve plans, no sales call
All plans include the same forensic checks. Pick the quota that matches your monthly document volume.
manualStarter
30 credits/mo
Manual spot-checks and integration testing
most commonGrowth
350 credits/mo
Active document processing pipelines
high volumePro
1,500 credits/mo
High-volume automation and API integrations
Enterprise (unlimited, on-premise available) — see full pricing
API key on signup. Free test environment on every plan. No card required.
Customer Stories
Teams that stopped document fraud
Compliance, finance, and risk teams use HTPBE? to catch manipulated PDFs before they become costly mistakes.
Caught an invoice where the total had been changed by less than a thousand dollars. Without this I would have approved it without a second look.
Sarah M.
AP Manager
United States
We had three applicants in the same week with bank statements that looked completely fine. Two of them were flagged as modified. You simply cannot see this by reading the document — it is in the file structure.
Lars V.
Risk Analyst, Online Lending
Netherlands
Salary slips were coming with altered figures. We identified two problematic files before the placement was finalised.
Priya K.
HR Operations Lead
India
Since we started checking documents this way, we stopped two applications early in the process that would have been very difficult to reverse later.
Julien R.
Fraud Analyst, Fintech
France
Some applicants were sending PDFs that looked authentic but had been edited in ways not visible to the eye. We now ask for checked originals when something is flagged. Already saved us from a few bad decisions.
Marta S.
Compliance Coordinator
Spain
One invoice was caught because there was a mismatch between the document dates and structure. That particular case would have cost us significantly.
Tariq A.
Finance Manager
United Arab Emirates
FAQ
Frequently asked questions
What’s the difference between ‘modified’ and ‘inconclusive’ for a contract?
modified verdict means the PDF structure contains forensic evidence of post-creation editing – revisions saved after the contract was first written, or changes made after signing. An inconclusive verdict means the contract was generated with consumer software (Microsoft Word, Google Docs) rather than a contract management or e-signature platform. For contracts, inconclusive means HTPBE? cannot confirm the file as an untouched original – a prompt for manual review against your own executed copy, not proof of fraud.Can it detect clause changes if no digital signature was used?
certain), but HTPBE? detects post-creation modifications on unsigned contracts too. It flags contracts edited after they were generated, contracts reworked outside the software that produced them, and dates that disagree with each other. Most contract fraud involves unsigned PDFs or PDFs where the signature page is kept intact while the body is changed.Does it check the identity of signatories?
How does it handle contracts with multiple revision versions?
Secure your workflow
Create your account – check PDFs on the web or with an API key, both ready on signup.
No sales call. Cancel any time.