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Internal Fragmentation vs. External Fragmentation: What's the Difference?

Edited by Janet White || By Harlon Moss || Updated on October 5, 2023
Internal fragmentation refers to wasted space within allocated memory blocks, while external fragmentation occurs when free memory is scattered throughout, preventing the allocation of contiguous space for data.

Key Differences

Internal fragmentation and external fragmentation both pertain to the wastage of memory in computer storage but differ in their locales and causes. Internal fragmentation occurs when allocated memory is partially used, causing the unused portion to be wasted. Conversely, external fragmentation happens when free memory blocks are scattered, causing an inability to satisfy the contiguous memory request.
When discussing internal fragmentation, one must consider the unused memory that resides within an allocated block, hence making it unavailable for other processes or data. External fragmentation, on the other hand, describes a condition where available memory is separated into small, non-adjacent blocks, hindering the allocation of a larger, contiguous block of memory.
The resolution strategies for internal fragmentation and external fragmentation are distinct. Internal fragmentation can often be mitigated by utilizing memory allocation algorithms that minimize leftover space, like Best Fit. To address external fragmentation, techniques like memory compaction, which reorganizes memory to create larger contiguous blocks, may be employed.
In internal fragmentation, waste is generally due to the allocation strategies that allocate slightly more memory than required. With external fragmentation, memory waste results from allocating and deallocating memory blocks of various sizes, which eventually scatter available memory.
Internal fragmentation typically occurs in systems that utilize fixed-size allocation units, wherein partially used units waste memory internally. External fragmentation, in contrast, is more prevalent in systems that allow dynamic memory allocation, where memory is allocated and deallocated in varied block sizes.

Comparison Chart


Waste within an allocation unit.
Waste due to scattered free memory.


Fixed-size memory allocation.
Dynamic memory allocation.


Utilize precise allocation strategies.
Use memory compaction.

Impact on System Performance

May lead to unnecessary memory waste.
May prevent allocation of larger blocks

Memory Access

Memory is accessed but not fully utilized.
Memory is available but not contiguous

Internal Fragmentation and External Fragmentation Definitions

Internal Fragmentation

It represents the phenomenon of memory wastage inside allocated spaces.
Detecting internal fragmentation early prevented potential bottlenecks in the system.

External Fragmentation

It denotes the condition wherein memory waste happens between allocated spaces.
Pervasive external fragmentation hindered the system from efficiently managing memory.

Internal Fragmentation

It pertains to the inefficiency of memory usage within an allocated region.
Developers sought to minimize internal fragmentation to optimize memory utilization.

External Fragmentation

External fragmentation implies available memory is not contiguous, complicating allocation.
Addressing external fragmentation improved the system's ability to allocate larger memory blocks.

Internal Fragmentation

Internal fragmentation implies wasted memory segments confined within allocations.
Algorithms minimizing internal fragmentation significantly enhanced the program’s efficiency.

External Fragmentation

It signifies a state where free memory exists but is fragmented across the storage.
The database faced challenges due to persistent external fragmentation in memory allocation.

Internal Fragmentation

Internal fragmentation refers to unused memory spaces within allocated blocks.
The application experienced delays due to internal fragmentation wasting crucial memory.

External Fragmentation

External fragmentation means memory availability in separated, non-adjacent blocks.
Memory compaction techniques alleviated issues caused by external fragmentation.

Internal Fragmentation

Internal fragmentation entails having unusable memory spots within assigned blocks.
The internal fragmentation within the system led to suboptimal memory usage.

External Fragmentation

External fragmentation involves scattered, unusable memory blocks throughout storage.
Due to external fragmentation, the software couldn’t allocate a contiguous memory block.


How does external fragmentation occur?

External fragmentation occurs when free memory blocks are scattered throughout the system, preventing contiguous space allocation.

How can internal fragmentation be minimized?

Utilizing memory allocation strategies that allocate only the needed memory can minimize internal fragmentation.

How do operating systems typically handle internal fragmentation?

Operating systems might utilize allocation strategies that attempt to closely match memory requests to minimize internal fragmentation.

Can external fragmentation be prevented entirely?

Completely preventing external fragmentation is challenging, but it can be minimized with algorithms and memory compaction techniques.

Can external fragmentation occur in any memory allocation strategy?

Yes, external fragmentation can occur in various memory allocation strategies, especially with dynamic allocation.

Can we recover memory from external fragmentation?

Yes, through memory compaction, which rearranges memory, larger contiguous blocks can be formed to recover from external fragmentation.

Can external fragmentation be mitigated without system downtime?

Some systems may allow online memory compaction, but often, resolving external fragmentation effectively might require downtime.

What’s a notable difference between internal and external fragmentation?

Internal fragmentation deals with wasted space within allocated blocks, while external relates to non-contiguous free memory blocks.

Which is more problematic: internal or external fragmentation?

Both can be problematic in different scenarios; internal for wasting memory and external for preventing larger memory allocations.

Is internal fragmentation dependent on specific memory allocation strategies?

Yes, internal fragmentation is more common in fixed-size allocation strategies due to the consistent block size.

Can external fragmentation lead to system crashes?

In extreme cases, external fragmentation may prevent essential memory allocations, potentially leading to system instabilities or crashes.

How does external fragmentation impact storage management?

External fragmentation makes storage management challenging by preventing the allocation of contiguous blocks, even when sufficient memory exists.

How does internal fragmentation influence memory allocation in real-time systems?

Internal fragmentation might lead to inefficient memory usage, which can be critical in real-time systems with stringent resource requirements.

Is internal fragmentation prevalent in dynamic memory allocation?

It can occur, but it’s typically more associated with fixed-size allocation where excess space in a block is wasted.

Is paging effective against internal fragmentation?

Paging can still experience internal fragmentation if allocated pages contain unused space, though it might be minimized.

How does memory compaction alleviate external fragmentation?

Memory compaction consolidates free memory into a single contiguous block, thereby reducing external fragmentation.

Can a system be optimized to avoid both internal and external fragmentation simultaneously?

Certain strategies may minimize both, but trade-offs may occur as methods to reduce one type may inadvertently increase the other.

What is internal fragmentation?

Internal fragmentation refers to the waste of memory within allocated blocks due to allocating slightly more than needed.

What's a common cause of internal fragmentation?

Fixed-size memory allocation, where memory blocks may not be fully utilized, commonly causes internal fragmentation.

Does internal fragmentation affect system performance?

Yes, internal fragmentation can lead to inefficient memory usage, affecting overall system performance.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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