What is the ERR file format?
.err files are used for application monitoring and diagnostic purposes.
.err files store plain-text error messages generated by an application or operating-system process. Errors can occur during application launch, resource loading, compilation, or writing data to files, among others. .err files are commonly used during the testing phase - for both functional tests and edge-case testing where software is exercised in extreme conditions, such as access to severely limited resources or unexpected user inputs. They are equally valuable for troubleshooting deployed applications.
.err files store data in plain text and can be opened with any text editor. They are generated automatically by applications, often under a timestamped or unique name that makes it easy to trace which run or update produced them. An empty (zero-byte) .err file alongside a job's output usually means no errors occurred - a common convention in batch-processing and build systems.
Each line typically identifies a source location (file and line number), an error code, and a human-readable message. The exact structure depends entirely on the tool that wrote it; there is no single specification for the format.
Security & safety
RISK: LOWA plain-text .err can't execute and is safe to open in a text editor. Two real cautions: (1) error files can contain sensitive data - file paths, usernames, SQL with values, connection strings - so scrub them before posting publicly or attaching to a forum; (2) be wary of a file with a double extension (errors.err.exe) pretending to be an error log - that is an executable, not text. Old/empty .err files are generally safe to delete; a 0-byte .err usually just means "no errors".
Format details
in a nutshell- Oracle SQL*Loader / utility error file - Oracle SQL*Loader (sqlldr) and other Oracle utilities write rejected rows and error messages to a .err / .bad file during data loads.
- Compiler / build error output - Many compilers and build tools (e.g. C/C++, FoxPro COMPILE, LaTeX) dump build errors to a .err file beside the source.
- Genome assembly error reads - Some bioinformatics/EDA tools also emit .err diagnostic files; readable as text but specific to that pipeline.
Programs that open ERR files
Windows3 apps
Notepad
Open-source Open the .err; handles large files and lets you search for 'error'/'fail'. Best free choice. 
macOS1 app
Linux1 app
gedit / nano / less
Open-source Open in gedit, or in a terminal use less file.err (/error to search, G to jump to the end). Technical details
deep spec| Format type | Plain-text error/diagnostic log |
| Encoding | ASCII or UTF-8 (locale-dependent; set by the producing application) |
| Compression | None (rotated copies sometimes stored as .err.gz) |
| Typical size | 0 bytes (no errors) to a few MB; often only a few lines |
| Associated OS | Cross-platform (Windows, macOS, Linux, Unix) |
| MIME type | text/plain |
| Line structure | Typically: source location (file:line), error code, and human-readable message per line |
| Specification | None - format is entirely defined by the producing program; no universal standard |
| Generation | Automatically created by compilers, databases, build tools, and applications |
| Empty file meaning | A zero-byte .err next to a job's output conventionally means no errors occurred |
| Naming convention | Often timestamped or uniquely named per run to allow tracking across multiple builds or updates |
| Related formats | .log (general log), .out (standard output), .dmp (crash dump), .wer (Windows error report) |
| Opening tools | Any text editor; specialized log viewers (glogg, Notepad++) add filtering for large files |
| Released | Convention as old as software error reporting itself |
| Open standard | Yes · royalty-free |
ERR conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about ERR files.
Frequently asked questions
What is an ERR file?
How do I open an ERR file?
less on Linux. It's just text - you read it, you don't run it.My ERR file is empty (0 bytes) - is that a problem?
Can I delete ERR files?
Why is my ERR file full of strange characters?
Where do ERR files come from?
command 2> errors.err).
