Glossary → Software & Firmware Terms
What Is a Boot Loop?
When a phone repeatedly restarts without ever completing startup — stuck showing the logo over and over.
Definition: A boot loop is when a phone continuously restarts without completing the startup process — stuck showing the Apple logo or brand logo, then restarting, endlessly. The phone never reaches the home screen. Usually caused by corrupted firmware, a failed OS update, or a hardware fault.
Fix sequence to try
Step 1 — Hard Reset: Hold the correct button combination to force restart. Sometimes clears a temporary boot loop from a crashed process.
Step 2 — Recovery Mode (iPhone): Connect to iTunes/Finder and choose Update first — reinstalls iOS without erasing data. Only choose Restore if Update fails.
Step 3 — DFU Mode (iPhone): Deeper firmware restore bypassing the bootloader. Last software option.
Step 4 — Hardware diagnosis at PhoneDoctor: If all software attempts fail, the boot loop is caused by hardware — logic board fault, storage chip failure, or water damage. Free diagnostics.
Software vs hardware boot loops
Software boot loops (failed update, corrupt OS) are resolved by Recovery Mode or DFU restore. Hardware boot loops (storage chip fault, logic board damage) survive every software restore attempt — the phone enters Recovery Mode but restore fails with error codes like 4013, 4014, or error 9. These require board-level repair.
Related terms
→ Hard Reset — always the first step with a boot loop
→ Recovery Mode — second step for boot loops on iPhone
→ DFU Mode — last software option before hardware diagnosis
→ Logic Board — hardware fault behind boot loops that survive software restores
Boot loop that won’t resolve with software fixes?
PhoneDoctor diagnoses hardware boot loops — storage chip faults and board-level repair. Free diagnostics, walk-in welcome.