How to open a code or text file online
Three steps, a few seconds, no software.
Open your .ASM file
Drop it on the box, choose it from your device, or paste the text straight in.
View it instantly
Your .ASM file opens neatly formatted with line numbers.
Search, copy or download
Search the text, jump to any line, then copy what you need or download a clean copy.
What is a .ASM file?
Plain text that programs, servers and people write every day.
An ASM file is assembly language source code - a plain-text file of low-level CPU instructions. Open it in any text editor to read or edit it. To run the code, assemble it with NASM, MASM, or GNU as into an object file, then link it into an executable. Note that some CAD programs (Pro/ENGINEER, SolidWorks) also use .asm for binary 3D assembly documents - those are unrelated to source code.
Programs that open .ASM files
| Full name | Assembly Language Source Code File |
|---|---|
| Developer | N/A (open text format; assembler syntax varies by toolchain — MASM, NASM, GAS, ARM as) |
| First released | 1940s-1950s (assembly languages); .asm convention popularized by DOS/MASM era (1980s) |
| Category | Text & Code |
| MIME type | text/x-asm |
Related viewers
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Frequently asked questions
Is my .ASM file uploaded anywhere?
No. The file is read and highlighted for you.
Why do some characters look wrong (é, ł)?
That usually means the file was saved in one encoding and opened in another. We detect UTF-8, UTF-16 and the Windows-1250/1252 code pages automatically and show which one was used.
Can it handle huge log files?
Yes, up to 50 MB. Only the lines on screen are drawn, so scrolling stays smooth. Syntax colours are switched off for files over 1.5 MB to keep things fast.
How do the log level filters work?
We find levels like ERROR, WARN, INFO and DEBUG on each line. Lines without a level, such as stack traces, stay with the entry above them, so filtering to errors keeps the full trace.
Can I edit the file?
This is a viewer. To change code, download it or copy it into your editor. Converting encodings and line endings is planned.
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