NSURLErrorServerCertificateUntrusted (-1202) — iOS/macOS

Enterno.io Editorial Team

NSURLErrorServerCertificateUntrusted: iOS Fix

By Anatoly Oshmanovsky · Updated Apr 18, 2026

Key idea:

NSURLErrorServerCertificateUntrusted (code -1202) — the iOS/macOS Foundation Network layer rejected the server SSL cert. Cause: self-signed, expired, untrusted CA, empty SAN, or cert does not satisfy ATS (App Transport Security) requirements. In 2026 iOS requires TLS 1.2+, forward secrecy, SHA-256+ signature. Fix: real cert from Let's Encrypt/Sectigo, or for dev — NSAllowsArbitraryLoads (NOT production).

Below: causes, fixes, FAQ.

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Common Causes

Self-signed cert in dev without bundle trust
App Transport Security (ATS) rejects TLS 1.0/1.1
Cert missing SAN (Subject Alternative Name) — iOS requires since 2017
CA not in iOS trust store (legacy Symantec roots retired)
Incomplete cert chain (missing intermediate)

Step-by-Step Fix

Use a real cert from a mainstream CA (Let's Encrypt, DigiCert, Sectigo)
Check chain: Enterno SSL Checker
For dev: pin cert in-app via NSURLSessionDelegate urlSession:didReceiveChallenge:
Info.plist: NSAppTransportSecurity > NSExceptionDomains for a specific domain (careful)
Server TLS config: TLS 1.2+ + ECDHE + SHA-256

Check SSL Certificate →

Related SSL Errors

CertificateExpiry, issuer, domains (SAN)

ChainIntermediate and root CA validation

TLS ProtocolTLS version and cipher suite

VulnerabilitiesHeartbleed, POODLE, weak ciphers

Why teams trust us

TLS 1.3

supported

Full

CA chain check

<2s

result

30/14/7

days-to-expiry alerts

How it works

Enter domain

TLS chain verified

Expiry date & vulnerabilities

What Does the SSL Check Cover?

SSL/TLS is the encryption protocol that protects data between the browser and server. Our tool analyzes the certificate, chain of trust, TLS version, and knownvulnerabilities.

Certificate Details

Issuer, validity period, signature algorithm, covered domains (SAN), and validation type (DV/OV/EV).

Chain of Trust

Full chain verification: from leaf certificate through intermediates to root CA.

TLS Analysis

Protocol version (TLS 1.2/1.3), cipher suites, Perfect Forward Secrecy (PFS) support.

Expiry Alerts

Set up a monitor — get Telegram and email alerts 30/14/7 days before expiration.

DV vs OV vs EV Certificates

DV (Domain Validation)

Confirms domain ownership only
Issued in minutes automatically
Free via Let's Encrypt
Suitable for most websites
Most common certificate type

OV / EV

Organization (OV) or Extended Validation (EV)
Issued in 1-5 business days
Costs $50 to $500/year
For finance, e-commerce, government sites
Increases user trust

Who uses this

DevOps

SSL certificate monitoring

Security

TLS config audit

SEO

HTTPS as ranking factor

E-commerce

customer trust

Common Mistakes

❌

Expired certificateBrowsers block sites with expired SSL. Set up auto-renewal or monitoring.

❌

Incomplete certificate chainWithout intermediate CA, some browsers and bots cannot verify the certificate.

❌

Mixed content on HTTPS siteHTTP resources on an HTTPS page — the browser lock icon disappears, reducing trust.

❌

Using TLS 1.0/1.1Legacy TLS versions have known vulnerabilities. Use TLS 1.2+ or 1.3.

❌

Domain mismatch in certificateThe certificate must cover all site domains, including www and subdomains.

Best Practices

✓

Set up auto-renewalLet's Encrypt + certbot with cron — certificate renews automatically every 60-90 days.

✓

Enable HSTSStrict-Transport-Security header forces browsers to always use HTTPS.

✓

Use TLS 1.3TLS 1.3 is faster (1-RTT handshake) and safer — legacy ciphers removed.

✓

Monitor expiration datesCreate a monitor on Enterno.io — get notified well before expiration.

✓

Verify chain after renewalAfter certificate renewal, confirm that intermediate certificates are installed.

Get more with a free account

SSL certificate monitoring, check history and alerts 30 days before expiry.

Learn more

Research

TLS 1.3 Adoption 2026: Growth Pace

Errors

Frequently Asked Questions

Allow self-signed in dev?

Info.plist → NSAppTransportSecurity → NSExceptionDomains → your-dev-domain → NSExceptionAllowsInsecureHTTPLoads=YES. Debug builds only.

Certificate pinning best practice?

SHA-256 cert hash or SPKI pin. Rotate with the cert, validate on every build.

iOS ignores self-signed?

Yes, Foundation by default. Needs a custom trust eval via URLSessionDelegate.

ATS requirements 2026?

TLS 1.2+, ECDHE forward secrecy, AES-128-GCM+, SHA-256 signature. Cert with SAN (mandatory).